We now have a single tree-sitter grammar. The quarto-markdown-pandoc crate has been changed to support it.

This is a full rewrite, and so the changes are unfortunately substantial. However, the new tree-sitter grammar is:

• unambiguous (no conflict rules)
• fine-grained and semantic: most pandoc nodes are directly tracked
• a single tree-sitter grammar: opens the chance of doing incremental parsing (though this is likely hard and currently completely unimplemented)

The APIs in quarto-markdown-pandoc don't change at all.