Add WebSocket support

**Is your feature request related to a problem? Please describe.**
I would like to request WebSocket support for Azure Static Web Apps. I understand there are current API constraints that prevent this. I have an Angular app that calls my API, hosted in Azure App Service, which uses SignalR. That API has endpoints like "/api/hubs/messages" that the client can connect to and get SignalR messages.

When trying to connect, my client gets the following error message:
```
Error: Failed to start the connection: Error: Unable to connect to the server with any of the available transports. Error: WebSockets failed: Error: WebSocket failed to connect. The connection could not be found on the server, either the endpoint may not be a SignalR endpoint, the connection ID is not present on the server, or there is a proxy blocking WebSockets. If you have multiple servers check that sticky sessions are enabled. ServerSentEvents failed: Error: 'ServerSentEvents' is disabled by the client. LongPolling failed: Error: 'LongPolling' is disabled by the client.
```

**Describe the solution you'd like**
I would like to be able to call "/api/hubs/messages" and have it connect to my SignalR API hub.

**Describe alternatives you've considered**
I could try ServerSentEvents or LongPolling, but I really would like web sockets to work.