Add a shim for grep-edit

[gs-101]

grep-edit is a major mode introduced in Emacs 31 (introduced in commit db1eb8a2) which enables the editing of Grep results, by typing e in *grep* buffers. C-c C-c exits this mode and saves changes. It can be used as a built-in replacement of wgrep.

I can hold this PR back if it causes any issues in earlier versions.

[DogLooksGood]

Working on some improvements to simplify the shims at #664.

[gs-101]

Thanks, I'll checkout #664 and see if this PR is still necessary.

[DogLooksGood]

I think for now it's still necessary. But I want to remove the need somehow.

[gs-101]

Second force-push was because the commit had unintentional indentation changes.