Add release notes
Summary: This is a patial backport of Core PR14477 : https://github.com/bitcoin/bitcoin/pull/14477/commits/109699dd33c72539fc33619f7836b8088f63182c
Test Plan: Read.
Reviewers: #bitcoin_abc, majcosta
Reviewed By: #bitcoin_abc, majcosta
Differential Revision: https://reviews.bitcoinabc.org/D6137