Support for Android Test modules

I had some issues with adding screenshots to an existing test specific module.

https://developer.android.com/studio/test/advanced-test-setup#use-separate-test-modules-for-instrumented-tests

It looks like this is not supported by the plugin https://github.com/dropbox/dropshots/blob/main/dropshots-gradle-plugin/src/main/kotlin/com/dropbox/dropshots/DropshotsPlugin.kt
