Persist Application State

**Is your feature request related to a problem? Please describe.**
When closing and reopening the application, all state is lost (except the previously opened collection which is currently persisted using the settings manager, though that's not really the correct place for that implementation). When reopening the app, as a user I would expect the state to be the same as before the close (as in e.g. VS Code).

**Describe the solution you'd like**
- When the application closes, the renderer states are sent to the backend
- In the backend, the states are persisted using [electron-store](https://github.com/sindresorhus/electron-store)

**Describe alternatives you've considered**

**Additional context**