Include newer PHP and MW versions in CI

[alistair3149]

Also mark MW master as experimental

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.07%. Comparing base (00e7753) to head (2c5c0a6).
⚠️ Report is 8 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##             master     #280   +/-   ##
=========================================
  Coverage     74.07%   74.07%           
  Complexity      399      399           
=========================================
  Files            47       47           
  Lines          1292     1292           
=========================================
  Hits            957      957           
  Misses          335      335           

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[malberts]

master branch seems a bit useless now, because it's failing before even getting to the tests.