docs: adds google analytics tag

[lukegalbraithrussell]

Summary

We've got a working GA property now! This adds the tag to the site for those sweet sweet page views.

Requirements (place an x in each [ ])

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.07%. Comparing base (a455807) to head (8231fd5).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2191   +/-   ##
=======================================
  Coverage   82.07%   82.07%           
=======================================
  Files          18       18           
  Lines        1545     1545           
  Branches      443      443           
=======================================
  Hits         1268     1268           
  Misses        179      179           
  Partials       98       98           

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