Unsupported KaTeX macros

[fwkoch]

• \empty - KaTeX treats \empty as \emptyset. (In LaTeX, though, \empty seems a little overloaded... Maybe it's fine if we lean into KaTeX support in this case?)
• \lbrace/\rbrace - these do the same as \left\{/\right\} - there are equivalent KaTeX macros for other symbols, e.g. \lparen
• \textbf - many KaTeX bold and italic commands are not supported - this should be simple, we already support \bf
• \hline/\hdashline - I think we will need to use typst #line for these - hopefully easy for simple, full-width horizontal line. I imagine converting lines might get more complex for other cases.
• \begin{cases} - https://typst.app/docs/reference/math/cases/