refs https://github.com/TryGhost/Ghost/issues/9505
- wire up the link button in the toolbar to set a `linkRange` property on `{{koenig-editor}}`
- add `{{koenig-link-input}}` that is shown when `{{koenig-editor}}` has a `linkRange` set
- <kbd>Escape</kbd> will cancel the link input
- clicking outside the input will cancel the link input
- previously selected text will be re-selected on cancel
- if an existing link was selected (or partially selected) then pre-fill the link input with the `href`
- `X` is shown when there's a href value and clicking will clear the input
- <kbd>Enter</kbd> *with* a href value will remove all links from text that is touched by the selection and create a new link across only the selected text
- <kbd>Enter</kbd> *with no* href value will remove all links touched by the selection
- fixed toolbar tick positioning that was 8px off after change to Spirit classes
