chore: checkpoint before Python removal

vendor/matchers/README.md

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+# matchers
+
+Regular expression matching on Rust streams.
+
+[![Crates.io][crates-badge]][crates-url]
+[![Documentation][docs-badge]][docs-url]
+[![MIT licensed][mit-badge]][mit-url]
+[![CI][ci-badge]][ci-url]
+
+[crates-badge]: https://img.shields.io/crates/v/matchers.svg
+[crates-url]: https://crates.io/crates/matchers
+[docs-badge]: https://docs.rs/matchers/badge.svg
+[docs-url]: https://docs.rs/matchers/0.2.0
+[mit-badge]: https://img.shields.io/badge/license-MIT-blue.svg
+[mit-url]: LICENSE
+[ci-badge]: https://github.com/hawkw/matchers/actions/workflows/ci.yml/badge.svg
+[ci-url]: https://github.com/hawkw/matchers/actions/workflows/ci.yml
+
+## Overview
+
+The [`regex`] crate implements regular expression matching on strings and byte
+arrays. However, in order to match the output of implementations of `fmt::Debug`
+and `fmt::Display`, or by any code which writes to an instance of `fmt::Write`
+or `io::Write`, it is necessary to first allocate a buffer, write to that
+buffer, and then match the buffer against a regex.
+
+In cases where it is not necessary to extract substrings, but only to test whether
+or not output matches a regex, it is not strictly necessary to allocate and
+write this output to a buffer. This crate provides a simple interface on top of
+the lower-level [`regex-automata`] library that implements `fmt::Write` and
+`io::Write` for regex patterns. This may be used to test whether streaming
+output matches a pattern without buffering that output.
+
+Users who need to extract substrings based on a pattern or who already have
+buffered data should probably use the [`regex`] crate instead.
+
+[`regex`]: https://crates.io/crates/regex
+[`regex-automata`]: https://crates.io/crates/regex-automata