feat: offline lists

[Supamiu]

Is your feature request related to a problem? Please describe.
When trying to create very large lists, the website becomes slower and goes slower and slower with new items added to the list.

Describe the solution you'd like
As the slowness comes from the fact that the list is connected to a realtime database, having a way to create "offline" lists could be nice.

Describe alternatives you've considered
Splitting the list in multiple ones.

Additional context
Would only be on desktop app, as it needs file system to handle big lists, or evaluate LocalStorage for this, without reaching its limits.

[ayyaruq]

Def in favour of LocalStorage, even if it's only in desktop app, since that uses the filesystem anyway and could later be extended to browser too.