Update docs for startup page of configuration
Summary: After several resurfaces of GUI the current docs are not up-to-date.
Test Plan: I used an impression from D11382 to write this. Tested with checkXML5. An updated screenshot is needed.
Reviewers: Dolphin, ngraham
Reviewed By: Dolphin, ngraham
Subscribers: ngraham, kfm-devel, kde-doc-english
Tags: Dolphin, Documentation
Differential Revision: https://phabricator.kde.org/D29220