Proxy SignalR -- document how

Using Yarp proxy SignalR, I frequently encounter connection failures, about 10 requests out of 3 failed, but ocelot did not encounter this situation

Below is my routing configuration
```json
{
"Routes": {
"SignalRRoute": {
"ClusterId": "SignalRCluster",
"CorsPolicy": "CorsPolicy",
"AuthorizationPolicy": "JwtPolicy",
"Match": {
"Path": "/BaizeHub/{*any}"
},
"Transforms": [
{
"PathRemovePrefix": "/BaizeHub"
},
{
"RequestHeadersCopy": "true"
},
{
"RequestHeaderOriginalHost": "true"
},
{
"RequestHeader": "Upgrade",
"Set": "WebSocket"
},
{
"RequestHeader": "Connection",
"Set": "Upgrade"
},
{
"X-Forwarded": "Set",
"For": "Append",
"Proto": "Append",
"Prefix": "Append",
"HeaderPrefix": "X-Forwarded-"
}
]
}
},
"Clusters": {
"SignalRCluster": {
"LoadBalancingPolicy": "PowerOfTwoChoices",
"Destinations": {
"Message/Destination1": {
"Address": "https://172.30.50.13:5400"
},
"Message/Destination2": {
"Address": "https://172.30.50.12:5400"
}
},
"HttpClient": {
"DangerousAcceptAnyServerCertificate": true
},
"HttpRequest": {
"Version": "1.1",
"Timeout": "00:10:00"
},
"HealthCheck": {
"Active": {
"Enabled": "true",
"Interval": "00:00:10",
"Timeout": "00:00:10",
"Policy": "ConsecutiveFailures",
"Path": "/Health"
},
"Passive": {
"Enabled": true,
"Policy": "TransportFailureRate",
"ReactivationPeriod": "00:00:10"
}
}
}
}
}
```

- Yarp.ReverseProxy 1.0.0-preview.12.21328.2
- Linux