[Feature] Better Image and Video Support

**Is your feature request related to a problem? Please describe.**
I'd like better support for rendering images and videos in Kepler.
The issues right now:
* No video support
* Large images (1080p+) don't fit on the page
* It's not discoverable/an extra thing to remember to set the column name
as `` to render images

**Describe the solution you'd like**
* Kepler automatically renders URLs that end in .png|.jpeg as `` elements
* Kepler automatically renders URLs that end in .mp4 as `` elements
* Kepler renders columns with name `` as `` elements
* Kepler enforces CSS style height: 200px on these elements so that large (1080p+)
assets are rendered in a reasonable manner

**Describe alternatives you've considered**
I haven't considered alternatives, but I am open to suggestions.

**Additional context**
I've made these changes in a fork of kepler and they work well, so I'd be interested in
contributing them back to the main fork.