Add support for basic generic types

[ZacSweers]

Resolves #9. This works by introducing a new FieldType class that allows for defining type arguments to the raw type.

Along the way I did a few opportunistic things

• Improved the primitive type handling and matching to use KP constants
• Added more tests around nullability
• Simplified "optional" handling by just deferring it to the code gen rather than the gradle property, which is now deprecated.
• Checked in yarn.lock, which kotlin JS generates and is otherwise re-generated per-device building this repo.

I looked at adding something to the README, but in the process I noticed much of the README seems to be out of sync (possibly with past updates), where the java and kotlin code snippets don't actually match up with their output buildconfig files. I'd rather leave that to a separate issue if that's ok.

I couldn't find any formatting tooling or styles in the repo, so I tried to best-effort match.

[gmazzo]

Thanks @ZacSweers! I used your ideas and combined them into the following PR #100, trying to keep the original signature of the DSL.

I still need to adjust a few things, but the PoC is working fine.

[gmazzo]

Checked in yarn.lock, which kotlin JS generates and is otherwise re-generated per-device building this repo.

Actually, I've just added this to the .gitignore file, does it really need to the checked on the source code? As it's generated by Kotlin/JS tooling and not needed for the repo to build, I usually just ignore this file.