Add simple filter box for icons

[nburka]

Adds a box to filter icons by their name.

To test:

• enter a few letters from the name of any icon
• both the category for the icon and the icons that match should show up
• erase the search and try other matches

[nburka]

For some reason I don’t understand, when I try removing letter from the filter, it gets super-slow. I’m obviously doing something wrong… I thought maybe it was modifying the categories prop and then re-firing the iconsToRender despite how I’m using the useMemo, but I’m not sure.

To Test:

• enter “I” “U” “D”
• then remove each character “D” “U” “I” (once you’re down to one character is really slow)