Add commands to interact with the plugin

[mbedded]

Some ideas:

• Reload view: View could be refreshed via command (or button). Especially useful if the settings are invalid, instead of close/reopen the view.
• Create new task: Add a simple dialog to create a new task. It should be as minimal as the dashboard. So the flow could be "command > enter text > return > dialog closed". Users are able to create new todos on-the-fly without switching contexts.

Linked to #6 (Checklist)