Implement Jetstream Support

[TheRipperoni]

This creates an additional service that can be used as an alternative to the firehose subscriber. Advantage being significantly less bandwidth consumption as well as cpu time.

It also allows for customizing which lexicons you want to specifically query.

[rudyfraser]

Couple small changes I'd like you to take a look at for main.rs but then otherwise should be good to go. Thanks for getting started on this!

[rudyfraser]

Oh, one other thing. Because this is a jetstream-subscriber and not meant as a jetstream implementation could you rename the package as such? Wouldn't want there to be a namespace clash down the line if someone wanted to implement jetstream in the future for rsky.

[TheRipperoni]

Oh, one other thing. Because this is a jetstream-subscriber and not meant as a jetstream implementation could you rename the package as such? Wouldn't want there to be a namespace clash down the line if someone wanted to implement jetstream in the future for rsky.

Updated to rename the package to rsky-jetstream-subscriber, as this make it much more clear what it does