[Feature Request]: Add support for trigger type of assignee only

[rytswd]

Enhancement Area

Issue Comment Event Handling, Comvent Configuration YAML, Runtime

Details

Add another trigger type of Assignee only. This allows more dynamic updates to who can trigger Comvent to kick off based on each issue.

It is likely that the runtime will need to parse the event payload, which means extra GitHub Action usage, but that is probably a good start.