Reorganize language bindings

* Move rust binding: lib/binding -> lib/binding_rust
* Move wasm bindinig: lib/web -> lib/binding_web
* Add wasm readme

lib/binding_rust/helper.c

@@ -0,0 +1,17 @@
+#if defined(TREE_SITTER_TEST)
+
+void ts_record_free(void *);
+
+void rust_tree_sitter_free(void *p) {
+  ts_record_free(p);
+}
+
+#else
+
+void free(void *);
+
+void rust_tree_sitter_free(void *p) {
+  free(p);
+}
+
+#endif