Adjust compat bounds and CI Julia versions

[gdalle]

• Bump SWG version to 1.5.0
• Bump Julia compat to 1.6 instead of 1
• Add compat bounds to stdlib and test deps
• Update versions of GitHub actions
• Run CI on min, 1 and pre

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.15%. Comparing base (8128430) to head (01dbae6).

Additional details and impacted files

@@           Coverage Diff           @@
##           master      #51   +/-   ##
=======================================
  Coverage   95.15%   95.15%           
=======================================
  Files           9        9           
  Lines         475      475           
=======================================
  Hits          452      452           
  Misses         23       23           

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