Vendor dependencies

Let's see how I like this workflow.

vendor/anyhow/tests/test_autotrait.rs

@@ -0,0 +1,13 @@
+use anyhow::Error;
+
+#[test]
+fn test_send() {
+    fn assert_send<T: Send>() {}
+    assert_send::<Error>();
+}
+
+#[test]
+fn test_sync() {
+    fn assert_sync<T: Sync>() {}
+    assert_sync::<Error>();
+}