Header to not HSH

[Th4nat0s]

X-GitHub-Request-Id: C561:71A05:1027E40:10585CC:69218E59
X-Fastly-Request-ID: f1271990bf630f317be33e46e46b83674e173c56

[Th4nat0s]

Fixed in acab4f2.

Added masking for volatile GitHub/Fastly headers before smart hashing:

• X-GitHub-Request-Id
• X-Fastly-Request-ID

Also added regression coverage, release notes, and README update.

Validation run:

• PYTHONPATH=src python3 -m unittest discover -s tests
• black --check
• pylint

[Th4nat0s]

Closing via acab4f2.