Rename dotfiles -> briefcase

Renaming my mono-repo briefcase.

I first introduced this commit in master, but it introduced a bug where one of
two things would happen:

1. Emacs wouldn't start and would crash X.
2. Emacs would start but my keyboard wouldn't work.

I learned some valuable debugging skills in the process. Here are some of them:

When my keyboard was broken, I wanted to control my computer using my
laptop. Thankfully this is possible by using `x2x`, which forward X events from
the SSH client to the SSH host.

```shell
> # I'm unsure if this is the *exact* command
> ssh -X desktop x2x -west :0.0
```

Git commit-local bisecting. I didn't need to do a `git bisect` because I knew
which commit introduced the bug; it was HEAD, master. But -- as you can see from
the size of this commit -- there are many changes involved. I wanted to binary
search through the changes, so I did the following workflow using `magit`:

- git reset --soft HEAD^
- git stash 1/2 of the files changed
- re-run `nix-env -f ~/briefcase/emacs -i`
- restart X session
- If the problem persists, the bug exists in the non-stashed files. Repeat the
  process until you find the bug.

In my case, the bug was pretty benign. Calling `(exwm/switch "Dotfiles")` at the
bottom of `window-manager.el` was failing because "Dotfiles" is the name of a
non-existent workspace; it should've been `(exwm/switch "Briefcase")`.

There may have been more problems. I changed a few other things along the way,
including exposing the env vars BRIEFCASE to `wpcarros-emacs` inside of
`emacs/default.nix`.

The important part is that this was a valuable learning opportunity, and I'm
glad that I'm walking away from the two days of "lost productivity" feeling
actually productive.

README.md

@@ -1,17 +1,16 @@
-# dotfiles
+# briefcase
 
-This is my mono-repo. Having a personal mono-repo is a new idea for me, so at
-the time of this writing, the state of this repository is fledgling.
+Welcome to my briefcase: my monorepo.
 
-I'm attempting to amass a collection of functions across a variety of languages
-while minimizing the costs of sharing the code across a projects. Stay tuned for
-more updates as my definition of the mono-repo becomes more clear, my opinions
-evolve, and my preferences change.
+I'm attempting to amass a collection of packages that span a variety of
+languages while minimizing the costs of sharing the code. This also includes
+configuration for things like emacs, tmux, ssh, and other tools.
 
-My configuration also lives inside of my mono-repo. Things like Emacs, Tmux,
-SSH, and other tools are configured herein.
+# Installation (Deprecated)
 
-# Installation
+The installation instructions here are deprecated. I'd like to manage packaging
+and installing with Nix, but that is only partially supported at the
+moment.
 
 ## wpgtk and gvcci