Vendor dependencies

Let's see how I like this workflow.

vendor/wasm-bindgen-macro/ui-tests/invalid-attr.rs

@@ -0,0 +1,15 @@
+use wasm_bindgen::prelude::*;
+
+#[wasm_bindgen(x)]
+pub fn foo() {}
+
+#[wasm_bindgen]
+extern "C" {
+    #[wasm_bindgen(y)]
+    fn bar();
+
+    #[wasm_bindgen {  }]
+    fn bar();
+}
+
+fn main() {}