Add initial implementation of the file dropper

[FrozenAlex]

I ran prettier on it and it added too many formatting changes. Not the prettiest code out there but does the job

[WombleWoo7547]

lgtm

[Lauriethefish]

Mostly looking good although is there a reason why the mod importing logic in ModManager is reimplemented in DeviceModder? Ideally DeviceModder shouldn't involve mod installing and should just be installation management.

[Lauriethefish]

Mod importing logic now moved to ModManager. Needs a mod import queue to avoid race conditions where two separate drag-drops could cause two separate agent requests to be made simultaneously, which it will not handle gracefully. (it will likely handle it by shitting the bed)

[Lauriethefish]

Now lgtm