Block comment syntax for LilyPond API documentation

[Urs Liska]

We have thought for some time to develop a specification for API
documentation in LilyPond files. Mainly for library stuff, but it may
also be useful for "documents".

(There's some discussion you may read at
https://github.com/openlilylib/openlilylib/issues/109).

There seems to be an agreement to mainly use special block comments
preceding the documented function. The suggestion is

%{!
  Enter some documentation, maybe in *Markdown*,
  together with some fields in a to-be-discussed syntax.
%}

I think this is a good idea, reasonably similar to LilyPond's own block
comments. Before going that route I'd like to ask if anyone sees any
problems with that %{! syntax.
I can't really imagine because after the curly bracket LilyPond
considers this a comment, and so there's no significant risk that this
might interfere with any future parser expectations.
I'd just like to ask, just in case.

Best
Urs