add CHANGELOG for v1.20.1

[alimaazamat]

What type of PR is this?
/kind cleanup

What this PR does / why we need it:
Adds a changelog file for the impending CAPZ v1.20.1 patch

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

Special notes for your reviewer:

TODOs:

• squashed commits
• includes documentation
• adds unit tests
• cherry-pick candidate

Release note:

NONE

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 52.84%. Comparing base (532f5c7) to head (d9d4540).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5730   +/-   ##
=======================================
  Coverage   52.84%   52.84%           
=======================================
  Files         278      278           
  Lines       29610    29610           
=======================================
  Hits        15647    15647           
  Misses      13146    13146           
  Partials      817      817           

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[willie-yao]

/lgtm
/approve

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: 7c3cdb22374f5f31e69a45842be9120242aced4a

[mboersma]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: mboersma, willie-yao

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