refs https://github.com/TryGhost/Ghost/issues/9311
Koenig is being fully rebooted, first port of call is to focus on getting the rich-text only aspect of mobiledoc-kit working with our popup toolbar.
- renames old koenig implementation (used for reference, will eventually be deleted)
- new `{{koenig-editor}}` mobiledoc-kit component implementation based on ember-mobiledoc-editor
- markdown text expansions
- new `{{gh-koenig-edtor}}` that wraps our title+editor and handles keyboard navigation between the two
- clicks below content will focus the editor
- new `{{koenig-toolbar}}` component for the popup formatting toolbar with improved behaviour and simplified code
