Initial vendor packages

Signed-off-by: Valentin Popov <valentin@popov.link>

vendor/thiserror/tests/ui/source-enum-not-error.rs

@@ -0,0 +1,12 @@
+use thiserror::Error;
+
+#[derive(Debug)]
+pub struct NotError;
+
+#[derive(Error, Debug)]
+#[error("...")]
+pub enum ErrorEnum {
+    Broken { source: NotError },
+}
+
+fn main() {}