chore: checkpoint before Python removal

vendor/signal-hook-registry/README.md

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+# signal-hook-registry
+
+[![Actions Status](https://github.com/vorner/signal-hook/actions/workflows/test.yaml/badge.svg)](https://github.com/vorner/signal-hook/actions)
+
+This is the backend crate for the
+[signal-hook](https://crates.io/crates/signal-hook) crate. The general direct
+use of this crate is discouraged. See the
+[documentation](https://docs.rs/signal-hook-registry) for further details.
+
+## License
+
+Licensed under either of
+
+ * Apache License, Version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or
+   https://www.apache.org/licenses/LICENSE-2.0)
+ * MIT license ([LICENSE-MIT](LICENSE-MIT) or
+   https://opensource.org/license/mit)
+
+at your option.
+
+### Contribution
+
+Unless you explicitly state otherwise, any contribution intentionally submitted
+for inclusion in the work by you, as defined in the Apache-2.0 license, shall be
+dual licensed as above, without any additional terms or conditions.