Previously, the font-weight for 500 did not exist in our set, so
all of those examples defaulted to 400. This fixes them to stay
as they previously were by migrating them to a font weight of 400.
This fixes the styling to stay on the screen of most reasonably sized
monitors along with extending the JavaScript code to allow for the
video to be keyed to in the lightbox.
This adds an image feed that you can scroll through with hotkeys
in the lightbox.
The left and right arrow keys along with the left and right arrows
will go to the prev/next image, and clicking on an image will also
take a user to that image.
The child ".image-preview" has a background which is ordinarily
invisible (as it is the same color as the #lightbox_overlay bg,
however when fading in it is noticeable.