## Summary
This PR adds a basic README for the `ruff_python_parser` crate and
updates the CONTRIBUTING docs with the fuzzer and benchmark section.
Additionally, it also updates some inline documentation within the
parser crate and splits the `parse_program` function into
`parse_single_expression` and `parse_module` which will be called by
matching against the `Mode`.
This PR doesn't go into too much internal detail around the parser logic
due to the following reasons:
1. Where should the docs go? Should it be as a module docs in `lib.rs`
or in README?
2. The parser is still evolving and could include a lot of refactors
with the future work (feedback loop and improved error recovery and
resilience)
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Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
