For the unfamiliar, this is a major release and is what would be called "30.0" in a more typical version scheme (but Emacs uses x.0.y for prerelease versions).

As the email says at the bottom, here are the release notes: https://git.savannah.gnu.org/cgit/emacs.git/tree/etc/NEWS?h=...

What's new: https://www.masteringemacs.org/article/whats-new-in-emacs-30...

Or in antinews format: https://www.gnu.org/software/emacs/manual/html_node/emacs/An...

Congratulations!

Personally though I've been running the igc branch... ;-)