Once installed, how do I configure a group menu?

The missing steps in the documentation are:
- Browse to a group page
- Click the "All Entities" tab
- Click the "+ Add new entity" button
- Click "Group Menu ({organization-name})"
- Fill in a Title
- Click the "Save" button

Attached a patch that updates the documentation with my steps above.

It's actually the group menu type name in the parentheses; updated the steps to match.

Patch in #5 RTBC.

+++ b/README.md
@@ -30,3 +30,17 @@ Note: Use of the module on a Composer managed site is also supported.
+1. Click the "+ Add new entity" button.

There's a group menu's tab we should reference instead of the all entities.