Arduino Esp8266 Signal(TIMER0_COMPA_vect) can’t compile
That instruction is for setting up an interrupt handler for the timer. It is very much specific to the AVR.
There's a lot more to do that just adjust that one statememt - you have to completely rewrite the whole of the timer code that you're using to operate with the ESP8266 SDK calls.
Without knowing what your code intends to achieve it's impossible to help you further, but this library may be of help to you.