Add Option to turn Insert key into PrintScreen

This is useful for users of ThinkPad laptops, which have the physical PrintScreen in between the right Alt and Ctrl keys. If you use "altwin:prtsc_rwin" to transform that key into a second Win key (which is quite useful), you lose your PrintScreen key. The new option being added here allows you to remedy that loss by making the Insert key into a PrintScreen key, for people who never use the Insert key.