chore: checkpoint before Python removal

vendor/libm/README.md

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+# `libm`
+
+A Rust implementations of the C math library.
+
+## Usage
+
+`libm` provides fallback implementations for Rust's [float math functions] in
+`core`, and the [`core_float_math`] feature. If what is available suits your
+needs, there is no need to add `libm` as a dependency.
+
+If more functionality is needed, this crate can also be used directly:
+
+```toml
+[dependencies]
+libm = "0.2.11"
+```
+
+[float math functions]: https://doc.rust-lang.org/std/primitive.f32.html
+[`core_float_math`]: https://github.com/rust-lang/rust/issues/137578
+
+## Contributing
+
+Please check [CONTRIBUTING.md](../CONTRIBUTING.md)
+
+## Minimum Rust version policy
+
+This crate supports rustc 1.63 and newer.
+
+## License
+
+Usage is under the MIT license, available at
+<https://opensource.org/license/mit>.
+
+### Contribution
+
+Contributions are licensed under both the MIT license and the Apache License,
+Version 2.0, available at <https://www.apache.org/licenses/LICENSE-2.0>. 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 mentioned, without any additional terms or conditions.
+
+See [LICENSE.txt](LICENSE.txt) for full details.