Support GraphQL subscriptions

[SydoxX]

Is your feature request related to a problem? Please describe.
GraphQL allows for subscriptions where data is pushed to the client rather than pulled by the client itself. This happens live via websockets which Grafana also supports.
I'm currently coding a live vehicle dashboard where data is fetched via GraphQL. A vehicle may drive or be stationary at any time so polling via GraphQL may just create unnecessary network traffic and load. With pushing via websockets traffic would only occur when a change in the data source happens.

Describe the solution you'd like
Simply changing any supported query from query to subscription should automatically open a websocket connection to the GraphQL endpoint. When one of the requested query value changes, the change should be immediately reflected on the dashboard without polling.

Describe alternatives you've considered
Grafana polling. Works but it always fetches data even when no new data is available at the source.