Adds a keymap for the frame-multiplexer.

[mychris]

I am not sure about the name of the *keymap* variable.

Currently, there is a lot of repetition in init.el. If the variable is named *keymap*, the user writes this into it's init.el to remap it:

(define-key *global-keymap* "C-v" lem/frame-multiplexer:*keymap*)

But now, the name of the keymap does not match the of the variable. But naming the variable *frame-multiplexer-keymap* introduces a lot of repetition in init.el

(define-key *global-keymap* "C-v" lem/frame-multiplexer:*frame-multiplexer-keymap*)

What do you think? What is the name of the keymap used for, is it just for user information?

[cxxxr]

I think *keymap* is a better reference here.
https://google.github.io/styleguide/lispguide.xml#Packages