UMBERTO BACCHI FROM offering refugees their spare rooms to donating cryptocurrency, people around the world have been using technology to channel help to Ukrainians since Russia launched its military assault last week. Some tech companies like Google and Microsoft have taken steps targeting Russian state media or helped start fundraising campaigns following Thursday's invasion, which the U.N. refugee agency said had forced more than half a million people to flee Ukraine. Here are five ways people and companies are using tech to help Ukrainians: 1) SPARE ROOMS AND FREE DOCTORS Home rental company Airbnb said on Monday its non-profit arm Airbnb.org would offer free, temporary housing for…