Support GraphQL subscriptions

[ndarilek]

Still fairly new to Elixir and Phoenix/Plug. Is this the appropriate repo on which to request support for GraphQL subscriptions?

There seems to be lots of work happening in this space recently:

• Apollo's subscription support just went live.
• Cashay also supports subscriptions.

I don't have an opinion/preference as to which approach is better. Maybe they're compatible. But Apollo at least seems to require Redis for multi-node deployments, a need which I imagine Elixir completely removes.