Rough underline, strikethrough, etc.

[Omikhleia]

(Moved from ptable.sile)

Since Aug. 2022 (or earlier, can't remember and lazy to check), the framebox package has an experimental and undocumented \roughunder command using a sketchy line(s) for a replacement of the "underline" command. As noted in-code:

This would need to be re-implemented and checked after multiline effects (e.g. multiline links and underline) are possibly added to the typesetter.

Such "liners" spanning multiple lines are making it in SILE develop branch for 0.15 and likewise in sile-x, which would allow to better implement this...

The command doesn't really belong to framebox, and should perhaps be moved to a dedicated package ("roughrules?")
There we could have:

• rough underline
• rough strikethrough
• rough highlight/mark and rough redacted text, see also Correctly implement highlight(mark)/insertions/deletions with styling support markdown.sile#110

[Omikhleia]

Caveat: re-introducing a silex.sile dependency on ptable.sile is probably a real bad idea, though.
Another path could be:

• Extract the rough logic as an independent luarocks (we are now close to having it feasible)
• Provide the above-mentioned commands in a new dedicated modules, that may depend on silex initially for compatibility, but can later get rid of it when switching to SILE 0.15+

Would make me maintain yet another rock, though...