Specs/HTML/2.0.0/Extensions/Gallery

The basic structure is as follows.

This gallery:

Renders as:

and  modes add some additional structure around

Attributes to support (on the extension tag):
 * showfilename
 * caption
 * mode
 * widths
 * heights
 * perrow

Renders as:

A more involved example:

Renders as:

A showfilename example:

Renders as: