areaDetector: create periodic jpeg image for liveview detector

# Feature Description

As a scientists i'd like to see a periodic image of my liveview detector in the web dashboard. One option is to create a jpeg from areaDetctor and then publish to web dashboard. The jpeg could also be saved with the data file to give a thumbnail option etc.

### Additional Information

areaDectector supports writing jpeg and spliting data flow to multiple plugins. Will need to see how to best make this periodic rather than all the time e.g. maybe enable/disable the plugin from another scanning record

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# Acceptance Criteria
- jpeg produced

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