Emitted when the editor can potentially be activated - this is for example when the current
note is changed, or when the application is opened. At that point you should check the
current note and decide whether your editor should be activated or not. If it should, return
true, otherwise return false.
Emitted when an editor view is created. This happens, for example, when a new window containing a new editor is created.
This callback should set the editor plugin's HTML using editors.setHtml, add scripts to the editor
with editors.addScript, and optionally listen for external changes using editors.onUpdate.
Required callbacks for creating an editor plugin.