Feature request: introduce XML comments

[WhitWaldo]

Especially as Metalama is capable of producing whole new properties, fields and methods to classes (and in the future hopefully, whole classes as well) and since the output can be consumed by other developers, it'd be ideal if there were some mechanism by which any of these introduced elements could also include comments passed through during compilation.

Especially on templates, it'd be great if I could just document the template itself and that carry through, but it'd be great if there were a programmatic means of doing so as well (e.g. when looping through a collection of types where it wouldn't make sense to put the same <see cref=""/> tags in the documentation).

Thank you for the consideration!