Continue gi.ts merge: Cleanups and updates

[JumpLink]

• Upgrade yarn to latest stable
• Upgrade dependencies to latest
• More Gir files added (copied from flatpaks)
• Update README.md
• Moved @ts-for-gir-test/types-packages package to new tests directory to allow more test packages
• Moved examples from examples/gjs to examples
• Cleanup examples
• Add bundler examples for Rollup and Parcel
• Bump version 4.0.0-beta.6

@ewlsh Still a work in progress but feel free to leave comments already