* add cmark lib, build succeeds
* building and running (with dupe asserts)
* list newlines, quote styles
* tables working in cmark
* fix table bg color math and code bg color
* code block highlighting only when theres a language
* share code block logic
* mentions need @
* update cmark lib
* shortlinks
* detect issue shortlinks
* simplify and correct shortlinks
* remove html comments
* tests passing