Update RELEASE-NOTES for 4.0.0

[JeroenDeDauw]

No description provided.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 60.00%. Comparing base (5a78276) to head (cc46418).
⚠️ Report is 3 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##             master     #136   +/-   ##
=========================================
  Coverage     60.00%   60.00%           
  Complexity      105      105           
=========================================
  Files             8        8           
  Lines           530      530           
  Branches         44       44           
=========================================
  Hits            318      318           
  Misses          171      171           
  Partials         41       41           

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