add exports to uninstall plugin

[ezio416]

now in a separate PR and improved a bit :)
implements #34

[codecat]

We may want to add more exports, if we want to make this something people can depend on. Just having 1 thing seems a little awkward.

Additionally, I question having 2 separate functions for the same purpose, one being an async version and one simply running the async version with startnew - I personally think we should leave that last part up to the plugin developer.

[ezio416]

I tried to think of other potential exports we might want but couldn't. Installing should probably only be done by the manager, I don't see a reason to export anything to do with the cache, and I don't see anything else that could be very useful

[ezio416]

bump :)

[codecat]

If this PR is just to get the cache sync to play nice on plugin removal, I think we need a different approach. Why not expose an export that calls PluginCache::Sync?