add initial skeleton for bitcoinfuzz

[brunoerg]

bitcoinfuzz is a project that does differential fuzzing of Bitcoin protocol and Lightning Network implementations. It currently addresses major and relevant implementations like Bitcoin Core, rust-bitcoin, LND, c-lightning, LDK and has a similar approach of cryptofuzz.

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[github-actions]

brunoerg is integrating a new project:
- Main repo: https://github.com/bitcoinfuzz/bitcoinfuzz.git
- Criticality score: 0.29250

[morehouse]

This project helps to secure projects throughout the Bitcoin ecosystem. With Bitcoin now exceeding $2T in market cap, I think this project is worth some of OSS-Fuzz's CPU cycles.