versioning: next version will be ripgrep 11
versioning: next version will be ripgrep 11

This sets up the release announcement and briefly describes the
versioning change. The actual version change itself won't happen until
the release.

Closes #1172

BurntSushi/ripgrep,BurntSushi/ripgrep,BurntSushi/ripgrep,BurntSushi/ripgrep