Vendor dependencies

Let's see how I like this workflow.

vendor/wasm-bindgen/tests/wasm/duplicate_deps.rs

@@ -0,0 +1,18 @@
+use wasm_bindgen::prelude::*;
+use wasm_bindgen_test::*;
+use wasm_bindgen_test_crate_a as a;
+use wasm_bindgen_test_crate_b as b;
+
+#[wasm_bindgen(module = "tests/wasm/duplicate_deps.js")]
+extern "C" {
+    fn assert_next_undefined();
+    fn assert_next_ten();
+}
+
+#[wasm_bindgen_test]
+fn works() {
+    assert_next_undefined();
+    a::test();
+    assert_next_ten();
+    b::test();
+}