Add GNOME/GTK Icon Development Kit

[bleonard252]

The icon set that GNOME and many Linux apps designed for GNOME use by default.

https://gitlab.gnome.org/Teams/Design/icon-development-kit/-/blob/main/src/icons.svg

Other related sets:

• The Adwaita icon set, consisting of GNOME system icons: https://gitlab.gnome.org/GNOME/adwaita-icon-theme/-/blob/master/src/symbolic/core.svg
• The "hairline" version of the Icon Development Kit: https://gitlab.gnome.org/Teams/Design/icon-development-kit/-/blob/main/src/hairline.svg

I'm not a maintainer of any of these sets, I'm an application developer who would like to use these icons to blend in to a system running GNOME, and in the past, Iconify has made using icons from various sets as needed easy.

Notes:

• The set is in one big SVG
• Each icon is in a second-level <g /> (the first-level groups are layers/sets, which icons are in)
• Each icon <g /> includes a <rect width=16 height=16 /> with fill:none
• #2e3434 is the default changeable color of most icons which should probably be replaced with currentColor
• Icons in these sets use opacity for shading
• Each icon has a <title /> with the actual icon title, and other tags are space-separated in the inkscape:label attribute
• A set prefix for the first could be idk or gnome, the second adwaita (or incorporated into the IDK set?), and the hairline IDK would be idk-hairline