Servo.h library missing fatal error

It appears that you’re compiling for simulation, but unfortunately you can’t simulate hardware devices:

Also, you are using the same digital pin (D0) for both your servo and button - each device needs to use a different pin. Specify a different pin for one of these devices, then try compiling and uploading to a board. D0 and D1 are used for serial communication with the IDE, so you may want to avoid using these pins for devices in your patches if you plan to use the debugger.