Addition of "ugrep" in comparison

[ax672d61]

Please add "ugrep", https://github.com/Genivia/ugrep, to the comparison.

[petdance]

What would be features that ugrep has that ack and ripgrep don't have?

[petdance]

The first place I want to put ugrep is over on https://altbox.dev.

Can you add some interesting info about ugrep at petdance/altbox#85 and then I can write up a page about it to go on altbox?