Add readme file for the api directory

See issue #5873

Docker-DCO-1.1-Signed-off-by: Timothy <timothyhobbs@seznam.cz> (github: https://github.com/timthelion)
Upstream-commit: 3e2b97ef26467228f6018e19f517ed535e107026
Component: engine

components/engine/api/README.md

@@ -0,0 +1,5 @@
+This directory contains code pertaining to the Docker API:
+
+ - Used by the docker client when comunicating with the docker deamon
+
+ - Used by third party tools wishing to interface with the docker deamon