fix: use full html page in show() for correct utf-8 display

[machow]

This PR addresses #414 by producing a full html page when using .show() to open a browser window. Previously, we only produced the table fragment, which for some reason caused the browser (or server) to screw up the encoding.

(The full html includes <meta charset="utf-8"/> which makes the encoding explicit)

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.

Project coverage is 86.75%. Comparing base (bacda7e) to head (ef25d8f).
Report is 67 commits behind head on main.

Files with missing lines	Patch %	Lines
great_tables/_export.py	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #458      +/-   ##
==========================================
+ Coverage   86.37%   86.75%   +0.38%     
==========================================
  Files          42       42              
  Lines        4683     4750      +67     
==========================================
+ Hits         4045     4121      +76     
+ Misses        638      629       -9     

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[machow]

shoot -- I need to fix a bit of code in our old blog post :/

[rich-iannone]

LGTM!

[rich-iannone]

Looks good, thanks!