html: add user data to context.

[kivikakk]

/cc @digitalmoksha

[github-actions]

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
./bench.sh ./comrak-23bae85	321.3 ± 0.9	319.9	323.4	2.96 ± 0.06
./bench.sh ./comrak-main	320.5 ± 5.9	316.9	347.3	2.95 ± 0.08
./bench.sh ./pulldown-cmark	108.6 ± 2.3	107.2	116.9	1.00
./bench.sh ./cmark-gfm	116.1 ± 7.8	112.8	153.6	1.07 ± 0.08
./bench.sh ./markdown-it	482.5 ± 3.3	476.8	493.1	4.44 ± 0.10

Run on Wed Mar 26 23:12:35 UTC 2025

[digitalmoksha]

Thank you @kivikakk! I'm hoping to have some time tomorrow to try and integrate it.

🙇 ❤️

[kivikakk]

Good luck! Let me know how it goes and if/when you might want a release with it!