Pull to sync

Currently, sync of a library needs to be triggered from the context menu of the library itself. If a user is not inside a library but e.g. inside a todo list, there is currently no way to easily start a sync.

To improve, we should:

• Have an option to trigger a sync also from sub-pages.
• Implement "pull to sync", as this is a well known gesture to start a sync as well and more useful on mobile devices.