feat: print emit response output if it's a cloudevent (#444)
feat: print emit response output if it's a cloudevent (#444)

The CloudEvent SDK will provide any event included in the response as a
return value from `Request()`. If it does, print it out. It makes the
experience nicer.

For example, if I run the default TypeScript event function locally, this
is what `kn emit...` looks like.

```
❯ ./func emit --sink local --data '{"hello": "world"}'
Context Attributes,
  specversion: 1.0
  type: echo
  source: function.eventViewer
  id: d7d81ccc-a365-4433-be6b-7edfa43ca360
  time: 2021-07-27T18:57:03.147Z
  datacontenttype: application/json; charset=utf-8
Data,
  {
    "hello": "world"
  }
```

Signed-off-by: Lance Ball <637094cbcafd6c4c397ebad24eca1a25fa2cf312@redhat.com>
knative/func,knative/func,knative/func,knative/func,knative/func,knative/func,knative/func