Fix Android Gradle packaging of files with '.' prefix

[horoni]

By default, Gradle ignores files prefixed with a dot. This caused a "Failed to unpack game assets, consider reinstalling the app" error on Android, because an entry for a file prefixed with a dot exists in integrity.txt but doesnt exist in the apk assets.

There is a dot prefix used in data/entity/binds. You can either rename it or merge my PR. Alternatively, should I open this PR against the main DDNet repository?

Checklist

• Tested the change ingame
• Provided screenshots if it is a visual change
• Tested in combination with possibly related configuration options
• Written a unit test (especially base/) or added coverage to integration test
• Considered possible null pointers and out of bounds array indexing
• Changed no physics that affect existing maps
• Tested the change with ASan+UBSan or Valgrind's memcheck (optional)
• I didn't use generative AI to generate more than single-line completions