more documentation in README about contents (#506)

README.md

@@ -14,6 +14,33 @@ Code Manager: Matthew Pyle
 For more information see the [Team
 Charter](https://docs.google.com/document/d/1uLbPx-pOWp7eECz_7VHRt_tQyD8PLFdrwo8dr4oMgjo/edit?usp=sharing).
 
+## Contents
+
+The rrfs-workflow code is organized in the following subdirectories:
+
+* doc - the User Guide documentation.
+* ecf - the ecFlow contents which will drive the RRFS workflow in NWS
+  operations.
+* fix - static data.
+* jobs - the main driver scripts (known as J-jobs) for each task. The
+  workflow driver (either ecFlow or rocoto) submits these J-jobs.
+* modulefiles - module files for NOAA HPC systems.
+* parm - parameter files - generally namelists or configure files.
+* scripts - the "ex scripts" - the primary script for a given task,
+  and called by the J-job.
+* sorc - all of the source codes that need to be built/compiled for
+  use within the package.
+* tests - unit tests for rrfs-workflow code.
+* ush - the utility scripts - scripts typically called by the "ex
+  scripts" to handle specific tasks, often repeatedly for different
+  times or geographic regions.
+* versions - shell scripts setting environment vars to the required
+  versions of all dependencies, for building and for running
+  rrfs-workflow.
+
+These are in compliance with the [NCO implementation standard]
+(https://www.nco.ncep.noaa.gov/idsb/implementation_standards/ImplementationStandards.v11.0.0.pdf).
+
 ## Build Instructions
 
 1. Clone the `main` branch of the authoritative repository: