Restucture wasm module, return a normal TSLanguage from load_language

lib/binding_rust/build.rs

@@ -35,6 +35,7 @@ fn main() {
         .flag_if_supported("-std=c99")
         .flag_if_supported("-Wno-unused-parameter")
         .include(src_path)
+        .include(src_path.join("wasm"))
         .include("include")
         .file(src_path.join("lib.c"))
         .compile("tree-sitter");