[request] Change in ArduinoLowPower DeepSleepExternalWakeUp example

[SebKister]

Summary

The current example demonstrating the external wake up from deep sleep uses the pin PC0. Unfortunately, this is also defined as the DEEP_SLEEP_ESCAPE_PIN in the escape_hatch function. If the user holds the wake-up switch low too long, it will not provoke a wake up but trigger the escape mechanism. The example could use the PA5 pin for example and clarify the role of PC0 in the wake up exit mechanism.