DOC: Module Code Structure

If there is anything we want to say about the code structure of modules, let's add it to our coding guidelines (or another location, if that seems better).

The following text was in our coding guidelines, but was not accurate, so it has been removed. We can use this as the starting point for what to improve, if we wish to add back this info at a later point...

The code structure of each module should be consistent. For example, most modules have the following folders:

• a store folder that contains store-related code
• a facade folder that contains all facade code for that particular module
• an occ folder that contains module-specific services that call the OCC APIs to communicate with the back end

The one exception is for UI components that are common to all modules, which are in storefrontlib/src/lib/ui/components.