Feature Request: Automated File Copying to Android Root Project in buildozer.spec

It is essential to introduce a dedicated section in the `buildozer.spec` file for copying files to the Android root project within the `.buildozer` directory. For instance, when working with Firebase, one needs to transfer the `google-services.json` file to the Android root project. However, the current process necessitates manual navigation through the `.buildozer` directory.

Start by tracing how buildozer.spec settings are handled in the .buildozer workflow, using google-services.json as the example input. Determine where the Android root project is prepared and define the configuration section and file-copy behavior; done means files specified there reach the Android root project without manual navigation.

Written by the indexing model from the issue text.