Support boilerplate for Elm clients

Lately I was toiling while writing a ClojureScript client. This made me crave
Elm. I'm going to rewrite the ClojureScript client using Elm, but along the way,
I'm stopping off here and recording my starter boilerplate.

boilerplate/elm/README.md

@@ -0,0 +1,17 @@
+# Elm
+
+Elm has one of the best developer experiences that I'm aware of. The error
+messages are helpful and the entire experience is optimized to improve the ease
+of writing web applications.
+
+## Developing
+
+If you're interested in contributing, the following will create an environment
+in which you can develop:
+
+```shell
+$ nix-shell
+$ elm-live -- src/Main.elm --output=Main.min.js
+```
+
+You can now view your web client at `http://localhost:8000`!