Build matrix

[whikloj]

GitHub Issue: n/a

What does this Pull Request do?

Adds a Github actions build file for the new 4.x branch.
Updates the Pull request template to stop using the invalid @Islandora/8-x-committers team.

What's new?

• Does this change require documentation to be updated?
• Does this change add any new dependencies?
• Does this change require any other modifications to be made to the repository (i.e. Regeneration activity, etc.)?
• Could this change impact execution of existing code?

How should this be tested?

This PR should run checks (and pass)

Interested parties

Tag (@ mention) interested parties or, if unsure, @Islandora/committers

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (4.x@df1c50c). Click here to learn what that means.
Patch has no changes to coverable lines.

Additional details and impacted files

@@          Coverage Diff           @@
##             4.x      #66   +/-   ##
======================================
  Coverage       ?   66.15%           
  Complexity     ?       25           
======================================
  Files          ?        4           
  Lines          ?      130           
  Branches       ?        0           
======================================
  Hits           ?       86           
  Misses         ?       44           
  Partials       ?        0           

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