Add a toggle to sync all collections

[dvanoni]

When enabling the collections to sync, can we have a toggle to sync all collections? Right now, we have to choose each single collection. Since I have a lot of collections, it seems time-consuming to do this.

Originally posted by @fredericky123 in https://github.com/dvanoni/notero/issues/58#issuecomment-1103511355

Please add an option to select "All Folders" so that synchronization applies to any new folders created in the library going forward?

Automatically syncing all current and future folders would improve the user experience by avoiding the need to manually select each new one.

Originally posted by @menelic in #374

For each library (i.e. the personal library and each group library), we should have an option to either sync the entire library or sync specific collections (as it is today).

[fredericky123]

Thanks!