Add copy-to-clipboard button to docs code blocks

[edrogers]

Add a copy-to-clipboard button for each code snippet on the docs page. Uses the Code Copy Button feature from the mkdocs Material theme

Fixes #184

Tasks

• Updated changelog.
• Updated documentation.

[JoshKarpel]

Sanity check - could you build the docs locally with mkdocs serve (https://www.spiel.how/contributing/) and make sure the copy buttons work?

[codecov]

Codecov Report

Base: 82.5% // Head: 82.5% // No change to project coverage 👍

Coverage data is based on head (30025b6) compared to base (b6d4582).
Patch has no changes to coverable lines.

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #185   +/-   ##
=====================================
  Coverage   82.5%   82.5%           
=====================================
  Files         33      33           
  Lines        843     843           
  Branches      96      96           
=====================================
  Hits         696     696           
  Misses       147     147           

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[edrogers]

Works for me!

(Colors modified and red circle added for emphasis)