Import cmake-mode.el and add cmake-font-lock submodule

* .emacs.d/init.el: require cmake-mode and cmake-font-lock.
* .emacs.d/lisp/cmake-mode.el: Import from upstream cmake repo as of
https://gitlab.kitware.com/cmake/cmake/-/blob/9daa244e9904e3d80afa149c927a01413e2a6cd0/Auxiliary/cmake-mode.el
into .emacs.d/lisp/ under the 3-clause BSD license.