feat: add the fmt_url() and fmt_email() formatting methods

[rich-iannone]

This PR adds the fmt_url() and fmt_email() formatting methods.

[codecov]

Codecov Report

❌ Patch coverage is 98.18182% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 98.33%. Comparing base (9c3c346) to head (b9fbbe9).

Files with missing lines	Patch %	Lines
great_tables/_formats.py	97.91%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #891      +/-   ##
==========================================
- Coverage   98.34%   98.33%   -0.01%     
==========================================
  Files          52       52              
  Lines        8200     8310     +110     
==========================================
+ Hits         8064     8172     +108     
- Misses        136      138       +2     

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