Add support for Material Design icons

[bitspittle]

trafficstars

Like Font Awesome icons, we could publish a library with Material Design icons.

See also:

• https://fonts.google.com/icons?selected=Material+Icons+Round
• https://materialdesignicons.com/

Marking this as good first issue since it's (hopefully) somewhat straightforward using the kobweb-silk-icons-fa module as reference.