Since tree sitter parsers output a c library, you could dynamically load it.

The rust bindings themselves are a thin ffi wrapper.

If you wanted to make it a little smoother than needing to compile the tree sitter syntax you could compile/bundle grammars up with wasm so its sandboxed and cross platform

Edit: found this vscode extension that dynamically loads syntaxes compiled to wasm. You should be able to do the same thing in rust: https://github.com/selfint/vscode-tree-sitter