Getting the :keyMap option to work for :editor/extra-codemirror-options

So, Code Mirror 5 has the “keyMap” option, however, to use the “vim” or “emacs” options you need to include extra code. I am working on doing this with the “:custom-js-url” setting, but I thought I should report what I have found.

It appears that there is in fact an “emacsy” option available by default in addition to the following: