Start a README in the github workflow directory.

Tweaks to docker readme.

Tweaks to main readme.

Signed-off-by: Jason Volk <jason@zemos.net>

docker/README.md

@@ -2,9 +2,12 @@
 
 All Docker images for the project are built here. All images are
 [Docker Bake](https://docs.docker.com/build/bake/) targets. All targets are leaves and
-branches of a unified tree leading to a single root. It is a massive combinatorial matrix
+branches of a unified tree leading to a single root. It is a combinatorial matrix
 of images from shared intermediate layers with a huge ever-growing pulsating cache.
 
+The result is the ability to run continuous integration for a number of build
+variations while only paying the cost of rebuilding the last layer for each one.
+
 ### Layout
 
 This directory is made up of four types of files.