Add GitHub Actions to build project automatically (#4)

.github/workflows/unity-exe-build.yml

@@ -0,0 +1,35 @@
+name: Unity Windows Build EXE
+
+on: push
+
+jobs:
+  build:
+    runs-on: windows-latest
+
+    steps:
+      - name: Checkout repo
+        uses: actions/checkout@v4
+
+      - name: Detect Unity version
+        id: unityVersion
+        run: |
+          $version = (Select-String -Path "ProjectSettings/ProjectVersion.txt" -Pattern "m_EditorVersion").Line.Split()[1]
+          echo "VERSION=$version" >> $env:GITHUB_ENV
+
+      - name: Build Windows 64-bit Player
+        uses: game-ci/unity-builder@v4
+        env:
+          UNITY_LICENSE: ${{ secrets.UNITY_LICENSE }}
+          UNITY_EMAIL: ${{ secrets.UNITY_EMAIL }}
+          UNITY_PASSWORD: ${{ secrets.UNITY_PASSWORD }}
+        with:
+          targetPlatform: StandaloneWindows64
+          unityVersion: ${{ env.VERSION }}
+          buildName: UberStrike.exe
+          buildPath: Build
+
+      - name: Upload Build Artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: WindowsBuild
+          path: Build/StandaloneWindows64