Idea: Sub-figures/tables, long captions, caption position

[Omikhleia]

The table and figure environment from the resilient.book class are pretty decent for a basic use case, but in a grander scheme, one could need

• Sub-tables / Sub-figures (= parts of the same figure, but have their own sub-level of numbering, their own captions, and are possibly presented side-by-side, etc. For instance, fig. 1 could contain fig. 1a and fig. 1b)
• Long vs. short caption (= the short caption comes first, is what is used in the list of figures/tables; the long caption shows only below the short-captioned fig/table; both can have different styles; e.g. the short caption "An example" shows as "Fig. 1 - An example" centered below the figure; the long caption can be a block-indented justified multi-paragraph blob).

[Omikhleia]

Additionally, we may want to investigate a styling option so that the (short only?) caption could be configured to be below or above the figures/tables. (Current state of art = always below)

Rationale: This type of feature has been requested on Typst, but it could be interesting for us here too in our own styling paradigm.
(Note that the "per-language" considerations could then perhaps also possibly be addressed via a base style as per #89.)