Feature freeze on the emacs-29 release branch

[Eli Zaretskii]

I think the release branch is now basically in good shape, and we can
start a full feature-freeze at this time.

>From now on, please install only bugfixes, preferably safe ones, on
the emacs-29 branch; all the rest should go to master.  Highest
priority is to fix recent regressions and issues with code that is new
in Emacs 29.  If you are uncertain whether a particular change belongs
to the release branch, please ask here.

The goal is to release the first pretest of Emacs 29.1 in a month or
so.

Let me take this opportunity to thank all those who worked hard since
the branching point to stabilize the branch, and in particular Yuan
and others who labored on the tree-sitter support (and continue to do
so).

Thanks.