refs https://github.com/TryGhost/Ghost/issues/9505
- use `ember-sticky-element` to stick card icons in top left when scrolling
- pass an `headerOffset` down from the `{{gh-editor}}` component through Koenig and the card components so that it can be used for adjustments where necessary
- calculate `headerHeight` in `{{gh-editor}}` any time we change the header class
refs https://github.com/TryGhost/Ghost/issues/9505
- use Spirit classes for card context menu
- add button and icon class options for context menu items
- add ability to have icon+text for context menu items
- add "Edit" context menu item to markdown and html cards
refs https://github.com/TryGhost/Ghost/issues/9505
- add `deleteCard` action to `{{koenig-editor}}` component and pass it through to the component cards
- required modifying the `_deleteCard` behaviour so that it doesn't always try to move the cursor
- use `onLeaveEdit` action from `{{koenig-card}}` in the markdown and html cards to check if their payload is empty and remove the card when exiting edit mode
- fixed `onLeaveEdit` action firing when card first rendered
refs https://github.com/TryGhost/Ghost/issues/9311
- wraps embed card in same container as the markdown card to handle mouse selection/edit toggles etc
- add render mode to embed card
- autofocus CodeMirror editor when switching to edit mode
- fix incorrect pointer on cards
refs https://github.com/TryGhost/Ghost/issues/9311
- add a basic HTML card that renders a CodeMirror editor
- adjust styles so that CodeMirror styles for the markdown editor don't affect CodeMirror instances inside Koenig
