Look into macro annotations to improve experience

[davesmith00000]

The inline def macro approach is serving me well in general but has a few shortcomings. I have hopes that we'll be able to do a better job with macro annotations because (I hope, I assume) we can annotate more than just defs.

Macro annotations are currently experimental, but they are available.

Doc link:
https://dotty.epfl.ch/api/scala/annotation/MacroAnnotation.html

A PR that defines addClass macros based on annotations, it's a good example:
scala/scala3#16534