broken reflink callback updates & big cleanup.

[kivikakk]

Fixes #143.

This PR moves the callback into the ParserOptions struct (which now takes a lifetime), and deprecates parse_document_with_broken_link_callback. It also cleans up the docs and some types in general.

[github-actions]

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
./bench.sh ./comrak-20a054b	328.5 ± 4.0	321.3	336.4	2.89 ± 0.05
./bench.sh ./comrak-main	334.1 ± 5.3	325.8	352.9	2.94 ± 0.06
./bench.sh ./pulldown-cmark	113.6 ± 1.3	111.2	116.1	1.00
./bench.sh ./cmark-gfm	121.5 ± 1.5	119.2	125.4	1.07 ± 0.02
./bench.sh ./markdown-it	502.3 ± 2.6	497.1	508.1	4.42 ± 0.05

Run on Thu Jul 11 12:45:33 UTC 2024