Release v0.3.0

[gadomski]

It feels slightly weird to release a new 0.X w/o any changes to the rust or cli crates, but I'm going to argue it's ok because

1. we don't expect to release this package too often once it settles, since its problem space is pretty small
2. complexity is much lower when we only have to manage one version for docs, etc

I took the liberty of adding myself to the authors 😊 @kylebarron lmk if you want on there as well.

[kylebarron]

It's fine to me to have a single version across Python and rust