Optimistic UI so the app feels faster

Currently the app seems to actually add events and wait for confirmation from the connected calendar. this has an negative affect on the UX as it seems unresponsive and slow. It would be great to have a more 'optimistic' approach to the UI, where the events are added within the app itself and then updated to the connected calendar in an async fashion as soon as possible. If it fails then you can show the user this or save the state and re-try.