diff --git a/js/package-lock.json b/js/package-lock.json
index 19d14da..5a32f88 100644
--- a/js/package-lock.json
+++ b/js/package-lock.json
@@ -1,6 +1,6 @@
 {
   "name": "jupyter-golden-layout",
-  "version": "0.3.0",
+  "version": "0.4.0",
   "lockfileVersion": 1,
   "requires": true,
   "dependencies": {
@@ -521,17 +521,6 @@
             "find-up": "^4.0.0"
           }
         },
-        "postcss": {
-          "version": "8.2.4",
-          "resolved": "https://registry.npmjs.org/postcss/-/postcss-8.2.4.tgz",
-          "integrity": "sha512-kRFftRoExRVXZlwUuay9iC824qmXPcQQVzAjbCCgjpXnkdMCJYBu2gTwAaFBzv8ewND6O8xFb3aELmEkh9zTzg==",
-          "dev": true,
-          "requires": {
-            "colorette": "^1.2.1",
-            "nanoid": "^3.1.20",
-            "source-map": "^0.6.1"
-          }
-        },
         "postcss-modules-extract-imports": {
           "version": "3.0.0",
           "resolved": "https://registry.npmjs.org/postcss-modules-extract-imports/-/postcss-modules-extract-imports-3.0.0.tgz",
@@ -2523,6 +2512,19 @@
         "postcss-value-parser": "^4.0.3",
         "schema-utils": "^2.6.6",
         "semver": "^6.3.0"
+      },
+      "dependencies": {
+        "postcss": {
+          "version": "7.0.36",
+          "resolved": "https://registry.npmjs.org/postcss/-/postcss-7.0.36.tgz",
+          "integrity": "sha512-BebJSIUMwJHRH0HAQoxN4u1CN86glsrwsW0q7T+/m44eXOUAxSNdHRkNZPYz5vVUbg17hFgOQDE7fZk7li3pZw==",
+          "dev": true,
+          "requires": {
+            "chalk": "^2.4.2",
+            "source-map": "^0.6.1",
+            "supports-color": "^6.1.0"
+          }
+        }
       }
     },
     "cssesc": {
@@ -4199,6 +4201,19 @@
       "dev": true,
       "requires": {
         "postcss": "^7.0.14"
+      },
+      "dependencies": {
+        "postcss": {
+          "version": "7.0.36",
+          "resolved": "https://registry.npmjs.org/postcss/-/postcss-7.0.36.tgz",
+          "integrity": "sha512-BebJSIUMwJHRH0HAQoxN4u1CN86glsrwsW0q7T+/m44eXOUAxSNdHRkNZPYz5vVUbg17hFgOQDE7fZk7li3pZw==",
+          "dev": true,
+          "requires": {
+            "chalk": "^2.4.2",
+            "source-map": "^0.6.1",
+            "supports-color": "^6.1.0"
+          }
+        }
       }
     },
     "ieee754": {
@@ -5180,12 +5195,6 @@
       "dev": true,
       "optional": true
     },
-    "nanoid": {
-      "version": "3.1.20",
-      "resolved": "https://registry.npmjs.org/nanoid/-/nanoid-3.1.20.tgz",
-      "integrity": "sha512-a1cQNyczgKbLX9jwbS/+d7W8fX/RfgYR7lVWwWOGIPNgK2m0MWvrGF6/m4kk6U3QcFMnZf3RIhL0v2Jgh/0Uxw==",
-      "dev": true
-    },
     "nanomatch": {
       "version": "1.2.13",
       "resolved": "https://registry.npmjs.org/nanomatch/-/nanomatch-1.2.13.tgz",
@@ -5672,14 +5681,28 @@
       "dev": true
     },
     "postcss": {
-      "version": "7.0.27",
-      "resolved": "https://registry.npmjs.org/postcss/-/postcss-7.0.27.tgz",
-      "integrity": "sha512-WuQETPMcW9Uf1/22HWUWP9lgsIC+KEHg2kozMflKjbeUtw9ujvFX6QmIfozaErDkmLWS9WEnEdEe6Uo9/BNTdQ==",
+      "version": "8.3.4",
+      "resolved": "https://registry.npmjs.org/postcss/-/postcss-8.3.4.tgz",
+      "integrity": "sha512-/tZY0PXExXXnNhKv3TOvZAOUYRyuqcCbBm2c17YMDK0PlVII3K7/LKdt3ScHL+hhouddjUWi+1sKDf9xXW+8YA==",
       "dev": true,
       "requires": {
-        "chalk": "^2.4.2",
-        "source-map": "^0.6.1",
-        "supports-color": "^6.1.0"
+        "colorette": "^1.2.2",
+        "nanoid": "^3.1.23",
+        "source-map-js": "^0.6.2"
+      },
+      "dependencies": {
+        "colorette": {
+          "version": "1.2.2",
+          "resolved": "https://registry.npmjs.org/colorette/-/colorette-1.2.2.tgz",
+          "integrity": "sha512-MKGMzyfeuutC/ZJ1cba9NqcNpfeqMUcYmyF1ZFY6/Cn7CNSAKx6a+s48sqLqyAiZuaP2TcqMhoo+dlwFnVxT9w==",
+          "dev": true
+        },
+        "nanoid": {
+          "version": "3.1.23",
+          "resolved": "https://registry.npmjs.org/nanoid/-/nanoid-3.1.23.tgz",
+          "integrity": "sha512-FiB0kzdP0FFVGDKlRLEQ1BgDzU87dy5NnzjeW9YZNt+/c3+q82EQDUwniSAUxp/F0gFNI1ZhKU1FqYsMuqZVnw==",
+          "dev": true
+        }
       }
     },
     "postcss-modules-extract-imports": {
@@ -5689,6 +5712,19 @@
       "dev": true,
       "requires": {
         "postcss": "^7.0.5"
+      },
+      "dependencies": {
+        "postcss": {
+          "version": "7.0.36",
+          "resolved": "https://registry.npmjs.org/postcss/-/postcss-7.0.36.tgz",
+          "integrity": "sha512-BebJSIUMwJHRH0HAQoxN4u1CN86glsrwsW0q7T+/m44eXOUAxSNdHRkNZPYz5vVUbg17hFgOQDE7fZk7li3pZw==",
+          "dev": true,
+          "requires": {
+            "chalk": "^2.4.2",
+            "source-map": "^0.6.1",
+            "supports-color": "^6.1.0"
+          }
+        }
       }
     },
     "postcss-modules-local-by-default": {
@@ -5701,6 +5737,19 @@
         "postcss": "^7.0.16",
         "postcss-selector-parser": "^6.0.2",
         "postcss-value-parser": "^4.0.0"
+      },
+      "dependencies": {
+        "postcss": {
+          "version": "7.0.36",
+          "resolved": "https://registry.npmjs.org/postcss/-/postcss-7.0.36.tgz",
+          "integrity": "sha512-BebJSIUMwJHRH0HAQoxN4u1CN86glsrwsW0q7T+/m44eXOUAxSNdHRkNZPYz5vVUbg17hFgOQDE7fZk7li3pZw==",
+          "dev": true,
+          "requires": {
+            "chalk": "^2.4.2",
+            "source-map": "^0.6.1",
+            "supports-color": "^6.1.0"
+          }
+        }
       }
     },
     "postcss-modules-scope": {
@@ -5711,6 +5760,19 @@
       "requires": {
         "postcss": "^7.0.6",
         "postcss-selector-parser": "^6.0.0"
+      },
+      "dependencies": {
+        "postcss": {
+          "version": "7.0.36",
+          "resolved": "https://registry.npmjs.org/postcss/-/postcss-7.0.36.tgz",
+          "integrity": "sha512-BebJSIUMwJHRH0HAQoxN4u1CN86glsrwsW0q7T+/m44eXOUAxSNdHRkNZPYz5vVUbg17hFgOQDE7fZk7li3pZw==",
+          "dev": true,
+          "requires": {
+            "chalk": "^2.4.2",
+            "source-map": "^0.6.1",
+            "supports-color": "^6.1.0"
+          }
+        }
       }
     },
     "postcss-modules-values": {
@@ -5721,6 +5783,19 @@
       "requires": {
         "icss-utils": "^4.0.0",
         "postcss": "^7.0.6"
+      },
+      "dependencies": {
+        "postcss": {
+          "version": "7.0.36",
+          "resolved": "https://registry.npmjs.org/postcss/-/postcss-7.0.36.tgz",
+          "integrity": "sha512-BebJSIUMwJHRH0HAQoxN4u1CN86glsrwsW0q7T+/m44eXOUAxSNdHRkNZPYz5vVUbg17hFgOQDE7fZk7li3pZw==",
+          "dev": true,
+          "requires": {
+            "chalk": "^2.4.2",
+            "source-map": "^0.6.1",
+            "supports-color": "^6.1.0"
+          }
+        }
       }
     },
     "postcss-selector-parser": {
@@ -6429,6 +6504,12 @@
       "integrity": "sha512-UjgapumWlbMhkBgzT7Ykc5YXUT46F0iKu8SGXq0bcwP5dz/h0Plj6enJqjz1Zbq2l5WaqYnrVbwWOWMyF3F47g==",
       "dev": true
     },
+    "source-map-js": {
+      "version": "0.6.2",
+      "resolved": "https://registry.npmjs.org/source-map-js/-/source-map-js-0.6.2.tgz",
+      "integrity": "sha512-/3GptzWzu0+0MBQFrDKzw/DvvMTUORvgY6k6jd/VS6iCR4RDTKWH6v6WPwQoUO8667uQEf9Oe38DxAYWY5F/Ug==",
+      "dev": true
+    },
     "source-map-resolve": {
       "version": "0.5.3",
       "resolved": "https://registry.npmjs.org/source-map-resolve/-/source-map-resolve-0.5.3.tgz",