Add simple mission statement

README.md

@@ -6,3 +6,8 @@ Install the following Arch Linux packages:
 * devtools
 ## Usage
 Run `make docker-image` as root to build the base image.
+## Purpose
+* Provide the Arch experience in a Docker Image
+* Provide the most simple but complete image to base every other upon
+* `pacman` needs to work out of the box
+* All installed packages have to be kept unmodified