fix(docs): update README.md, CHANGELOG.md with breaking change information about plugin registration

[artus9033]

Describe your changes

The plugin requires manual registration starting from v3.0.0, yet this information is not emphasized in the README, nor in the CHANGELOG.

Linked issues (if any)

N/A

Checklist before requesting a review

• E2E tests' snapshots (screenshots) are up-to-date
• documentation is up-to-date

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.49%. Comparing base (c553447) to head (c7bdd18).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #151   +/-   ##
=======================================
  Coverage   96.49%   96.49%           
=======================================
  Files          11       11           
  Lines         228      228           
  Branches      109      109           
=======================================
  Hits          220      220           
  Misses          8        8           

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