Vendor dependencies

Let's see how I like this workflow.

vendor/wasm-bindgen-macro/ui-tests/structural-and-final.rs

@@ -0,0 +1,11 @@
+use wasm_bindgen::prelude::*;
+
+#[wasm_bindgen]
+extern "C" {
+    type Foo;
+
+    #[wasm_bindgen(method, structural, final)]
+    fn bar(this: &Foo);
+}
+
+fn main() {}