add to the README.md file

Author: brent-insko-intel

README.md

@@ -12,6 +12,27 @@ It hosts public Issue tracker, and accepts patches (Pull Requests) from the
 general public.
 
 ## Directory Structure
+```
+BUILDING.md           Instructions for building the projects
+README.md             This file
+COPYING.md            Copyright and licensing information
+CODE_OF_CONDUCT.md    Code of Conduct
+external/             External code for projects in the repo
+include/              OpenXR platform include file
+specification/        xr.xml file
+src/                  Source code for various projects
+src/api_layer         Sample code for developing API layers
+src/loader            OpenXR loader code
+src/tests/            various test code (if looking for sample code start with hello_xr/
+```
+
+Currently the best sample code is in src/tests/hello_xr/.  More will be added in the future.  
+
+This structure is for the provisional specification.  Things are 
+incomplete at launch but will be added to going forward.
+
 
 ## Building
 
+See BUILDING.md
+