Explain where to get a template for a module contribution

contributing.rst

@@ -89,6 +89,17 @@ For example:
 
 If you are working on several things at the same time, try and keep things isolated in separate branches, to keep it manageable (both for you, and for reviewing your contributions).
 
+Contributing module documentation
+---------------------------------
+
+Your contribution to this repository will include a module documentation file. There are already several examples of these in the repository, but we provide a template for a generic module as a guide:
+
+.. toctree::
+    :glob:
+    :maxdepth: 1
+
+    ./modules/example_module/readme
+
 Checking your contribution locally
 ----------------------------------