List more open-source projects that use RGBDS for testing and statstical purposes

*Please comment with your projects' URLs that use RGBDS if you have them!*

Unlike #849, this would not be a new set of projects to add to CI: that's slow enough already, and most projects don't need to be built for every commit and PR.

However, it would be really nice to have a large suite of open-source GitHub repos (or GitLab, Sourcehut, etc) that we could use:

- There could be an optional script to build all the projects, which we could manually run before releases to make sure there's no unexpected breakage. (Probably a lot of projects would require patching their Makefiles or other build systems, but we have the testing capability for that.)
- We could analyze the source code to gauge which RGBDS features are heavily used, not used, used in combination, etc; as well as users' choices of symbol names, file structure, formatting, etc. This would be valuable information when we're deciding if+how to implement new features or deprecate+remove old ones. And it would be a less controversial option than any telemetry (not to mention not needing any networking code).