[clang-format] [NFC] add recent changes to release notes

Summary: clang-tidy keeps nice release notes of what is added, have clang-format do the same.

Reviewers: klimek, mitchell-stellar, sylvestre.ledru, sammccall

Reviewed By: mitchell-stellar

Subscribers: merge_guards_bot, Eugene.Zelenko, cfe-commits

Tags: #clang-format, #clang

Differential Revision: https://reviews.llvm.org/D70355