Use emoji in category names by default

[Siborgium]

Category support allows for emoji, which makes nice category list. Default config does not use them however as they may look broken if the user lacks necessary fonts, but on the other hand it's not immediately clear one may include them. Should we ship grid.conf with emoji by default?

[nwg-piotr]

Probably. In my golang implementation I just use the icon= value provided in corresponding file in desktop-directories file (like audio-video.directory). It's always worked for me.