Further publishing fixes

Fixes to repair poor pub.dev score:

- Fix `.pubignore` incorrectly excluding `lib/src/` from the published package.
- Declare platform support for Android, iOS, Linux, macOS, Windows, and Web.
- Update `hooks` to `^2.0.0`, `native_toolchain_c` to `^0.19.0`, `code_assets`
  to `^1.2.0`.
- Suppress ffigen-generated file warnings from pub.dev static analysis.

Emscripten fix in cicd