Support custom LSP

[joerdav]

I want to use helix but I can't seem to customise the LSPs.
The language is https://github.com/a-h/templ and contains it's own lsp under the command templ lsp, I tried adding an entry in my own languages.toml but it seems there is an enum that stops you from adding your own entry.

[pickfire]

Oh, seemed like you can't right now.

helix/helix-syntax/src/lib.rs

Lines 66 to 92 in 59f94d1

	mk_langs!(
	// 1) Name for enum
	// 2) tree-sitter function to call to get a Language
	(Agda, tree_sitter_agda),
	(Bash, tree_sitter_bash),
	(C, tree_sitter_c),
	(CSharp, tree_sitter_c_sharp),
	(Cpp, tree_sitter_cpp),
	(Css, tree_sitter_css),
	(Elixir, tree_sitter_elixir),
	(Go, tree_sitter_go),
	// (Haskell, tree_sitter_haskell),
	(Html, tree_sitter_html),
	(Java, tree_sitter_java),
	(Javascript, tree_sitter_javascript),
	(Json, tree_sitter_json),
	(Julia, tree_sitter_julia),
	(Php, tree_sitter_php),
	(Python, tree_sitter_python),
	(Ruby, tree_sitter_ruby),
	(Rust, tree_sitter_rust),
	(Scala, tree_sitter_scala),
	(Swift, tree_sitter_swift),
	(Toml, tree_sitter_toml),
	(Tsx, tree_sitter_tsx),
	(Typescript, tree_sitter_typescript)
	);

This requires support to use custom language name.

[archseer]

Yeah, we need to be able to define languages in languages.toml without binding them to tree-sitter.

[archseer]

With languages.toml no longer being tied to a tree sitter grammar, you should be able to define a custom language declaration now.