Image lightbox enhancements and fixes

[eric-schneider]

NOTE: This issue should probably be worked on in conjunction with #83.

We need to make some enhancements to the image lightbox (#68):

1. The lightbox doesn't currently support images that use the svg:: macro. This is problematic because we use this macro to support embedded SVGs that honor our CSS styles for light and dark mode (example).

2. We should probably add a background to the lightbox that's the same size as the image. Currently, images with transparent backgrounds look messy when overlaid on top of page content (example).
   

3. We need to be able to selectively turn off the lightbox for certain images (both block and inline images). We could probably handle this with a role similar to the remove-ext-icon role that we use for selectively disabling the external link icon.
   Currently, the lightbox is enabled for the badge icons on the Connection methods comparison page, which is a little silly:
   
   But more importantly, when we enable the lightbox for the svg:: macro, we'll need to be able to turn off the lightbox for the graphics on the landing page:
   

[eric-schneider]

1. The lightbox doesn't currently support images that use the svg:: macro. This is problematic because we use this macro to support embedded SVGs that honor our CSS styles for light and dark mode (example).

Our current lightbox library, zooming, doesn't support SVGs.

2. We should probably add a background to the lightbox that's the same size as the image. Currently, images with transparent backgrounds look messy when overlaid on top of page content (example).

Our new color tokens make this less noticeable, particularly in dark mode where the issue was most prevalent.

3. We need to be able to selectively turn off the lightbox for certain images (both block and inline images). We could probably handle this with a role similar to the remove-ext-icon role that we use for selectively disabling the external link icon.
   Currently, the lightbox is enabled for the badge icons on the Connection methods comparison page, which is a little silly.
   But more importantly, when we enable the lightbox for the svg:: macro, we'll need to be able to turn off the lightbox for the graphics on the landing page.

In a previous PR, we turned off the lightbox for inline images (image:). Taken together with the fact that we won't be supporting the lightbox for SVG images in the near future, this is basically non issues. We can always add a role when a greater need arises.

Given all of the above, I consider this issue closed.