build: release flow

[mcataford]

• Adds tag-based release flow. Create a new tag to trigger a release.
• Mentions release artifact availability in docs.

[codecov-commenter]

Codecov Report

Merging #2 (2e687c4) into main (fe31307) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main       #2   +/-   ##
=======================================
  Coverage   75.75%   75.75%           
=======================================
  Files           2        2           
  Lines          99       99           
=======================================
  Hits           75       75           
  Misses         24       24           

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