cli: Add command to send an event to endpoints
Add "swh webhooks event send [OPTIONS] EVENT_TYPE_NAME PAYLOAD_FILE" command to send a webhook message to endpoints listening for a specific event type.
Related to #6.
Staging instance, all changes can be removed at any time
Add "swh webhooks event send [OPTIONS] EVENT_TYPE_NAME PAYLOAD_FILE" command to send a webhook message to endpoints listening for a specific event type.
Related to #6.