Docs: “Global data files” should address non-camelCased filenames, name collisions

[Zearin]

The example on the Global data files uses a hypothetical file called _data/userList.json.

But what if...

• …the user has a data file named user-list.json instead?
  
• …there exists both a folder _data/users/ and the file _data/users.js?
  
  (This is a pretty common pattern, where top-level file’s name matches a folder name containing details )

Eleventy’s behavior in these cases should be documented.

[Zearin]

ping