feat(docs): add authroing instructions

docs/README.md

@@ -13,4 +13,18 @@ Another way to do local development without doing the Ruby setup steps is to use
 
 ```sh
 $ docker run -it --rm -v "$PWD":/usr/src/app -p "4000:4000" starefossen/github-pages
-```
+```
+
+# Authroing the docsite
+
+The docsite is a mix of stardoc generated markdown and hand written markdown.  
+The files marked with 
+```
+<!-- *********************
+ DO NOT EDIT THIS FILE
+  It is a generated build output from Stardoc.
+  Instead you must edit the .bzl file where the rules are declared,
+  or possibly a markdown file next to the .bzl file
+ ********************* -->
+ ```
+ Should be edited by modifying the docs in the source `.bzl` files, other files can be freely edited.