Lightweight enumerations and bullet lists

[Omikhleia]

I am proposing here a lightweight enumeration and bullet list package, with two aims in mind:

• At least partially address Provide nested enumerations and bullets #1106
• As teased in another ticket, improve the SILE manual so that bullet lists are now consistently typeset.

It is, actually, a "trimmed-down" version of the feature-rich but more experimental "enumitem" package I have in my own repository (https://github.com/Omikhleia/omikhleia-sile-packages). By "trimmed-down", I mean it doesn't use my experimental (and as-of-yet unfinished) "styles" system and has a bit less flexibility (with respect to customization, etc.). But otherwise it supports the same types of settings and has the same default general appearance (and also shares a good number of non-regression tests). So at this point at least, it's compatible with the things I have been using on my side for some months now.

As can be seen in the implementation, I tried to make it as robust as possible with respect to structure, paragraph skips, outer and inner parskips, as well as proper nesting. Regarding the latter, it supports two ways of nesting, a simple one (but less powerful) and a more powerful one (which, for the record, is what I now use for converted markdown in my unpublished proof-of-concept attempts, but at least you now know I tried to ensure I could use it in that context!).

Tuning the beast proved a bit hard, hence the number of tests. Are there too many tests? I can't say, except that each of them was added after I found a potential bug that wouldn't break the previous ones, or to check a documentation claim was indeed honored.

[alerque]

What happened to my review? I know I wrote up something for this a couple days ago ... 🤷 ... forgot to hit "send"? Still have the tab open somewhere?

[Omikhleia]

Moving on:

• Rebased on master + fixed conflicts at this date in affected package documentations and the manual.
• Renamed "lists" as per review (and settings also scoped to that namespace)
• Updated to resolve deprecation warnings (= updated to SILE.settings:*, class:formatCounter)

Next tasks to come:

• Rework the tests
• Add some additional options which prove useful for use in e.g. Markdown conversion

[Omikhleia]

Moving on:

• Tests reduced to 3
• Newly introduced options (custom bullet at itemize or item level; enumeration start and style override at enumerate level) allowed me to implement Markdown lists with all of Pandoc's subtleties on a separate project, so the package is kind of neater now ;)

[alerque]

Thanks for all the refactoring on this, and sorry it was such a long haul for a relatively simple thing. I'm much happier with the state now and think this package will get a lot of millage in the wild.