This one has an input to select the icon. It makes no sense to choose
an icon only by name, thus a <select> is not appropriate, and had to
use a hidden input with a row of button to choose the icon from. This
works now only because there are very few icons; we’ll need to choose
a different approach when there are many more icons.
Since now the icons have to be defined in CSS for both the public and
admin sections, i had to split it into a separate file that both sites
can use. I considered the option to “include” that CSS with m4, like
i do for images in demo.sql, but it made everything too complicated
(e.g., having to call make for each change in the CSS), and decided to
load that CSS in a separate <link>.
