Frigate 0.14 : keep thumbnail/snapshot for exported event in the export tab, generate thumbnail for clips exported from timeline

[hafx]

Describe what you are trying to accomplish and why in non technical terms In the "review" tab we have a thumbnail for each event with the image of the person/cat/dog/etc. provides a good indication of what triggered the event.

Describe the solution you'd like I would like to keep this thumbnail also when we export the event as well. Because once exported, the thumbnail is no longer the image with the person/cat/dog/etc.

Additional context I have also no thumbnail for clips exported from timeline manually. For example sometimes a person should be detected and I have no record for this event, I don't know why but in this case I have to export manually from the timeline if I want to keep a record.

Frigate version I just upgraded from 0.13 to 0.14