This change adds tree-sitter-less as an additional dependency, because we selfishly want to have nice highlighting for LESS files. Most of this change is infrastructure to add our own layer on top of tree-sitter-language-pack, letting us extend the list of supported languages and have our own fallbacks for getting language and parser objects. Testing Done: - Ran unit tests. - Ran update-language-info and update-queries scripts to generate the new data.