/api/v0 is deprecated on the gateway port

[d70-t]

Some functionality of ipfsspec (stat and ls) relies on accessing the (restricted) API through the gateway interface, this is no longer possible, because the /api/v0 endpoint has been removed. In the meantime, a lot of missing functionality has been added to the gateway, such that it's now likely possible to implement ipfsspec on top of regular gateway functionality (e.g. using the trustless gateway spec)