[RELEASE] Add v0.4.x

[adam2392]

Release v0.4.0

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• I've read and followed all steps in the Making a pull request
  section of the CONTRIBUTING docs.
• I've updated or added any relevant docstrings following the syntax described in the
  Writing docstrings section of the CONTRIBUTING docs.
• If this PR fixes a bug, I've added a test that will fail without my fix.
• If this PR adds a new feature, I've added tests that sufficiently cover my new functionality.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (9dcf913) 90.52% compared to head (4253386) 90.52%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #173   +/-   ##
=======================================
  Coverage   90.52%   90.52%           
=======================================
  Files          48       48           
  Lines        4020     4020           
=======================================
  Hits         3639     3639           
  Misses        381      381           

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