switch css unit rem rpx and px convert by keyboard shortcut.
⌥ + z (option + z) toggle px to rem
^ + z (control + z) toggle rpx to rem
alt+z toggle px to rem
win + z toggle rpx to rem
Default size for 1rem is 40px(750 design). It can be changed File->Preferences->Settings
remrpx.remEqual: set default size for 1rem
