fix(example): uses volatile for ISR variables

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: SuGlider

libraries/ESP32/examples/GPIO/FunctionalInterruptLambda/FunctionalInterruptLambda.ino

@@ -74,7 +74,7 @@ volatile bool ledStateChanged = false;    // Flag to indicate LED needs updating
 
 // Variables to demonstrate lambda captures
 volatile uint32_t totalInterrupts = 0;
-unsigned long lastInterruptTime = 0;
+volatile unsigned long lastInterruptTime = 0;
 
 // Debouncing variables (volatile for ISR safety)
 volatile unsigned long lastButton1InterruptTime = 0;