Add workflow to synchronise diseasyverse files

[RasmusSkytte]

Intent

This PR fixes #80

Approach

By using the Github action https://github.com/marketplace/actions/repo-file-sync-action, we should now be automatically be notified when files are out of sync and PRs should be created to ensure files are synced.

Known issues

This PR cannot be fully tested before merging, so issues may arrise after merging

Checklist

• The PR passes all local unit tests
• I have documented any new features introduced
• If the PR adds a new feature, please add an entry in NEWS.md
• A reviewer is assigned to this PR

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (b13a84f) 83.98% compared to head (748af9a) 83.98%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #82   +/-   ##
=======================================
  Coverage   83.98%   83.98%           
=======================================
  Files           8        8           
  Lines         843      843           
=======================================
  Hits          708      708           
  Misses        135      135           

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[RasmusSkytte]

These changes are solely related to workflows. PR review not needed here.