Dynamic Slideshow

[mohsin-r]

Closes #318.

You can now add a slideshow that supports all panel types (text, image, chart, map).

⚠️ Caution: This PR makes breaking changes to the current schema, so people should be comfortable with the design before this is merged. The details are in the files, but here are the changes that would be needed to migrate current products:

• For all the current slideshow panels, just change the type to image.
• For all the current image panels, add an images array and drop your single image config inside that array.

Essentially, the current image panels now support multiple images (similar to chart panels) and the slideshow panels support all panel types instead of just images.

Feel free to play around with creating, editing, viewing etc. slideshows and suggest changes to design, implementation, etc.

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This change is 

[mohsin-r]

Demo Link: https://ramp4-pcar4.github.io/storylines-editor/318/#/en/editor