Fix: Add trailing newline to CONTRIBUTING.md

[jeremyeder]

Issue: CONTRIBUTING.md is missing a trailing newline at the end of the file.

Request: Add a newline character at the end of CONTRIBUTING.md to comply with POSIX standards.

Details:

• File: CONTRIBUTING.md
• Change: Add a single newline at the end of the file
• Reason: Many tools expect files to end with a newline character

This is a simple, well-defined change.