Support for self-hosted websockets relay server

[matejdro]

Since push notifications support in Firefox appears to be at standstill, here is my idea for a workaround:

You already mentioned that web-sockets could work, but that would understandably cause huge costs if servers are hosted for you. But what if it is not hosted by you?

What if there would be a small self-contained relay that can run on raspberry PI or other low-cost computers? That relay would receive GCM messages and relay those messages to any connected websocket connections.

I know that would still leave majority in the dark, but it would still allow small subset of users to use the extension.