Fix android manifest generation: package name and screen

[enfipy]

• [x] Make resizeableActivity="true" in minimal AndroidManifest generator.
• [x] Rename android_app_id to android_package_name.
• [x] Write documentation for crossbundle metadata inside Cargo.toml.
• [x] Change version_code from string to u32.

Closes #71, closes #76.