[WIP] Add pattern request for certificate signing requests

[Copilot]

• Create test file with CSR sample from the issue (google.csr)
• Add CSR pattern to rsa/patterns.yml with experimental flag
• Update rsa/README.md with CSR pattern documentation
• Update main README.md to list CSR pattern
• Create snapshot file for validation
• Fix regex pattern to use correct number of dashes (-----)
• Fix test offsets to match actual pattern behavior
• Fix spelling error (commiting -> committing) in warning text
• All changes completed and reviewed

Original prompt

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This section details on the original issue you should resolve

<issue_title>Pattern Request: CSR</issue_title>
<issue_description>### Name / Description

A certificate signing request. These are not inherently secret leaks, but they might expose some metadata that is either sensitive or non-public.

Sample Snippets

True Positives

-----BEGIN CERTIFICATE REQUEST-----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-----END CERTIFICATE REQUEST-----

False Positives

[snippet]

[optional] Propose Solution

See RSA key samples for similar pattern, add CSR pattern to that section.
</issue_description>

Comments on the Issue (you are @copilot in this section)

Fixes #105

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