Assigning keyboard shortcuts is on you but the individual menu commands make that easy as pie. If you’ve not done this before Apple have instructions for setting shortcuts on a mac.
Why such a basic plugin? Right now Figma pastes retina images at their full pixel dimensions. If (like me) you find yourself scaling these by 50% an awful lot, a keyboard shortcut is a rather handy thing. Ideally the plugin would be called “Paste and scale” but triggering a system paste in a Figma plugin seems tricky or a no-go – contributions welcome