Add README

README files get a lot of exposure on GitHub, so they're a good way to draw in
contributors. This patch adds a short README with pointers to Wikitech for
interested contributors.

Change-Id: Ia0dca186713c7772f41560744cb0310e78a2e8a4

README

@@ -0,0 +1,15 @@
+The Wikimedia Foundation operates some of the largest collaboratively edited
+reference projects in the world, including Wikipedia. Our infrastructure powers
+some of the most highly-trafficked sites on the web, serving content in over a
+hundred languages to more than half a billion people each month. We use Puppet
+to manage our server configuration. This is our Puppet repository.
+
+For an overview of how we use Puppet, and a review of the code conventions and
+patterns that apply to this repository, see:
+https://wikitech.wikimedia.org/wiki/Puppet_coding
+
+The code in this repository is authored and maintained by Wikimedia engineers
+and a vibrant community of volunteer contributors. Get involved!
+
+https://wikitech.wikimedia.org/wiki/Get_involved
+freenode: #wikimedia-operations