signal a workflow

Example request

{
  "signalChannelName": "signalChannelName",
  "workflowRunId": "workflowRunId",
  "workflowId": "workflowId",
  "signalValue": {
    "data": "data",
    "extStoreId": "extStoreId",
    "extPath": "extPath",
    "encoding": "encoding"
  }
}