Feature Request - Allow SignalRTrigger in managed functions

**Is your feature request related to a problem?**
When trying to deploy SWA with managed functions that contains a SignalRTrigger, the deployment fails since the only supported trigger for SWA managed functions is HttpTrigger.

**Describe the solution you'd like**
Since SignalR service just seems to perform HTTP POST requests when handling upstream events it should be possible to use SignalRTrigger to simplify the inclusion of SignalR capabilities to the SWA.

**Describe alternatives you've considered**
A clear alternative would be to use "Bring your API" feature, or trying to mimic SignalRTrigger behaviour using HttpTriggers