Proposal: New info key `drracket:comments`

Things like DrRacket and Emacs offer commands to comment and un-comment a region.

Non-s-expression langs should be able to supply information for these commands, via a new info key named something like "drracket:comments".

Open to improvements, but initially I'll suggest the value is a list:

(list comment-start comment-end comment-padding)

where those three values as identical to three configuration variables in Emacs:

When a comment command makes a new comment, it inserts the value of
‘comment-start’ as an opening comment delimiter. It also inserts the
value of ‘comment-end’ after point, as a closing comment delimiter. For
example, in Lisp mode, ‘comment-start’ is ‘";"’ and ‘comment-end’ is
‘""’ (the empty string). In C mode, ‘comment-start’ is ‘"/* "’ and
‘comment-end’ is ‘" */"’.

The variable ‘comment-padding’ specifies a string that the commenting
commands should insert between the comment delimiter(s) and the comment
text. The default, ‘" "’, specifies a single space. Alternatively, the
value can be a number, which specifies that number of spaces, or ‘nil’,
which means no spaces at all.

Examples:

• s-expression langs (default): (";;" "" " ")
• scribble: ("@;" "" " ")
• rhombus: ("//" "" " ")

I'd suggest that when the key isn't supplied, it's OK to default to s-expression as the default. (Justification: There exist many more s-expression langs.)

Whatever the final form, I think the to-do list would be:

• Document at https://docs.racket-lang.org/tools/lang-languages-customization.html #635
• Add the info key to at least a few langs like:
  • scribble https://github.com/racket/racket/pull/4733
  • rhombus https://github.com/racket/rhombus-prototype/pull/348
• Revise DrRacket's (un)comment commands to use this.

If agreed/confirmed, I would probably be able to make PRs easily for all but the last. (I'm not familiar with that code. I'm not sure about details like whether a "Racket" menu is where these should continue to live.)

Background: https://github.com/greghendershott/racket-mode/pull/661#issuecomment-1693769408

Start by reviewing the documented language-customization page and DrRacket’s existing comment and uncomment commands, then compare the proposed drracket:comments values for s-expression languages, Scribble, and Rhombus. Done means confirming whether the documented info key and command integration are complete, or identifying the remaining design decision and implementation scope.