README: Add description

README.md

@@ -1,3 +1,13 @@
-slicer.org
-==========
+# slicer.org
 
+This project hosts the *new and experimental* slicer.org website currently served from http://slicer.github.io/slicer.org/.
+
+Transition to a new platform for managing and serving the Slicer top level page is happening on Slicer Discourse forum. See https://discourse.slicer.org/t/its-all-about-transitions-lets-talk-about-slicers-landing-page
+
+The `gh-pages` branch of this repository is configured as a [GitHub Pages](https://help.github.com/articles/configuring-a-publishing-source-for-github-pages/) source.
+
+# License
+
+It is covered by the Slicer License:
+
+https://github.com/Slicer/slicer.org/blob/master/LICENSE