Fix: Markdown linting issues

- Added newline at end of CONTRIBUTING.md (MD047)
- Added blank line after code fence in README.md (MD031, MD032)

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: challgren

CONTRIBUTING.md

@@ -241,4 +241,4 @@ Contributors will be recognized in:
 - Release notes
 - Project documentation
 
-Thank you for contributing to Aircraft Circle!
+Thank you for contributing to Aircraft Circle!

README.md

@@ -154,6 +154,7 @@ services:
     environment:
       - TAR1090_URL=http://tar1090:80
 ```
+
 - Filter by date range, pattern type, and callsign
 - Visual timeline of detection activity
 - Direct links to TAR1090 replay for each pattern