The emacs-28 release branch has been created

[Eli Zaretskii]

I've cut the emacs-28 branch, in preparation for the pretest of the
upcoming Emacs 28.1.

I encourage people who track the Emacs development to please switch to
this branch, build it and use it, so that any problems with it could
be reported sooner rather than later.

Barring any unexpected calamities, the first pretest of Emacs 28 will
be produced from this branch in a few weeks' time.