Merge in empires-html client

This HTML client for the empires game was originally developed in a
separate repository (and at the top-level).

In order to create this commit, I first rewrote the history of the
empires-html repository with:

	git-filter-repo --path-rename '':empires/

to move all of its content down into the empires sub-directory.

I then fetched things over to thi repository with:

	git fetch ../empires-html-filtered
        git merge --allow-unrelated-histories FETCH_HEAD

Going forward, we can develop the empires client within a
sub-directory of the lmno.games content (so they can share common
resources such as reset.css and style.css, etc.).