Guide page how to use with `-betterC`

[WebFreak001]

• [ ] how to define entry points
• [ ] what options to add to the recipe, also to keep it compatible as a library with other users
• [ ] link how https://code.dlang.org/?sort=updated&limit=20&category=library.nogc suitable for @nogc use might be usable
• [ ] mention bindbc-* packages and link to popular ones
• [ ] maintain a list of std packages compatible with betterC?

[renatoathaydes]

I suggest using tags for this. Those can probably be automatically inferred based on code analysis?

A package manager I like a lot is Dart's pub.dev which has something like tags to say whether a Dart package:

• uses the Dart SDK or require Flutter (the UI framework).
• minimum Dart SDK version.
• platforms (linux, macos, ios, windows, android, web).
• they used to have null-safe, but now all packages are null-safe.

DUB could infer the applicable data (@betterc, @safe, @nogc etc) for each package (perhaps as a percentage of all functions?), that would be really helpful.