Fix font lock in mhtml-ts-mode when the required tree-sitter grammars
are automatically installed (bug#79363). Also, cache tree-sitter indent
rules.
* lisp/textmodes/mhtml-ts-mode.el
(mhtml-ts-mode--treesit-font-lock-settings): Evaluate the rules only
after the tree-sitter grammars are installed.
(mhtml-ts-mode--treesit-indent-rules): Cache indent rules.
(mhtml-ts-mode): Call the new
`mhtml-ts-mode--treesit-font-lock-settings' function.
2ae54a8b17