I need to add external interrupt to my ESP

Hi guys
I am working on a project using ESP-01 with Blynk App to control a relay ON/OFF with GPIO0.

Is it possible to add an external bottom (as an interrupt )to change the state of the relay,ON to OFF or OFF to ON .

I am using the standard code from Blynk.

Yes, you should be able to attach an interrupt to GPIO2.
Or, you could use a timer to poll GPIO2 say every 100ms, which saves you having to do add a debounce routine to your ISR.