Enable lightbox by default

[richtabor]

Description

Closes #529 by enabling lightbox on by default for images.

Testing Instructions

1. Activate the theme.
2. Add a page.
3. Add an image.
4. See the "Expand on click" control active by default.
5. Add the "Clients" pattern.
6. Add an image to one of the placeholders.
7. See "Expand on click" turned off.

[richtabor]

Going to close this as not-planned. The lightbox feature needs a bit more attention before we should enable it by default out-of-the-box. This is a good PR to showcase the how though, for future reference.