Feature/begin without reset

[timschr]

Thank you for reviewing this pull request!
Scope of Change:
This PR introduces a new function, nfc.begin_without_reset(), to the Adafruit PN532 library, as well as a new example, esp32_deepsleep_interrupt.ino.
The new function allows the ESP32 (and potentially other platforms) to re-initialize the PN532 bus after deep sleep without resetting the PN532 chip.
The example demonstrates how to use this function to wake the ESP32 from deep sleep via the PN532 IRQ and immediately read the card that triggered the wakeup.
With the existing begin() function, this was not possible, as it resets the PN532 and loses the detected card state.
Known Limitations:
This approach assumes the PN532 remains powered during deep sleep and that the bus state can be safely re-initialized without a hardware reset.
If the PN532 is power-cycled or the bus is not preserved, this method may not work as intended.
The new function is primarily tested on ESP32 with SPI, but should be safe for other platforms as it only omits the reset/SAMConfig steps.
Testing:
The new example, esp32_deepsleep_interrupt.ino, was tested on ESP32-S3 hardware.
After deep sleep, the ESP32 can now read the card that triggered the IRQ wakeup, which was not possible with the original library.
Thank you for considering this contribution!
If you have any questions or need further changes, please let me know.