How do computers power so many lights on a keyboard?
LEDs do have a maximum current rating, but it does not mean they must be run at full power all the time. For this application at least two things can be used. Buy better, more efficient LEDs so that they light up brightly enough at lower current, say 1 mA or less. You can also divide the LEDs into multiple groups and multiplex them so that only one group is on at one given time and other groups are off. Sequentially turning on one group at a time at high enough scan rate creates an illusion of all LEDs being lit.