Add url tools example

[NA-V10]

Summary

Added a new example module url_tools under the examples/ directory.
It demonstrates URL encoding, decoding, and domain extraction using Python Fire.

Details

• New folder: examples/url_tools/
• Functions:
  • encode(text): URL-encode text
  • decode(text): URL-decode text
  • domain(url): extract domain from a URL
• Matches the format of existing examples (cipher, string_tools, etc.)
• Includes a complete test suite using testutils.BaseTestCase

Checklist

• [x] Example follows Google Apache header & format
• [x] Test file included
• [x] Functions exposed correctly via Fire
• [x] CLA already signed