Investigate if we could provide a project generator instead of using `cargo-mobile2`

There seems to be a fair bit of complexity around the generation machinery with `cargo-mobile2` that we could avoid. Maybe it would be better to provide a project generator that generates Xcode/Android projects that users could commit directly? This repo could then contain an example output of the generator.

However, while committing the Xcode/Android projects it generally useful for downstream app projects[^1], taking a template project and renaming everything is generally cumbersome, hence it might make this template repo less useful than it ought to be.

[^1]: Since they likely want to customize more things than we, or projects like `cargo-mobile2` with its `mobile.toml`, can anticipate, e.g. platform-specific app icons, entitlements etc.