Improve publish workflow

[teutoburg]

• Add improved version bump workflow action tested elsewhere.
• Improve build and publish workflow (painfully debugged elsewhere).

Again using this repo as a bit of a testbed.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (dddd9a9) 75.34% compared to head (7061329) 75.34%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master      #45   +/-   ##
=======================================
  Coverage   75.34%   75.34%           
=======================================
  Files           3        3           
  Lines         365      365           
=======================================
  Hits          275      275           
  Misses         90       90           

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