resolves mrusme/neonmodem#32 Filter for lemmy communities

[BreadMakesYouFat]

A possible fix for Lemmy community filtering. Tested with make + go1.19.0.

A limitation is that we currently only request 50 posts at a time, and so some communities will be empty. I tried naively upping the limit value but this seems to result in no results, so probably need to send multiple requests and I'm not very experienced with requests in go:

system/lemmy/lemmy.go
184:		Limit: types.NewOptional(int64(100)),  // This fails to retrieve any results.