Add link to examples in MicroPython repo

Author: lurch

README.md

@@ -2,6 +2,8 @@
 
 Examples to accompany the "[Raspberry Pi Pico Python SDK](https://datasheets.raspberrypi.org/pico/raspberry-pi-pico-python-sdk.pdf)" book published by Raspberry Pi Trading, which forms part of the technical documentation in support of Raspberry Pi Pico and the MicroPython port to RP2040.
 
+**Note:** There are also additional examples for the RP2040 port of MicroPython [here](https://github.com/micropython/micropython/tree/master/examples/rp2) in the upstream [MicroPython repo](https://github.com/micropython/micropython).
+
 ## Contributions
 
 While we welcome pull requests to contribute further example code, please do not link to personal sites or to your social media. Contributions which are fully documented with an AsciiDoc description and a Fritzing wiring diagram, e.g. see the [NeoPixel Ring](https://github.com/raspberrypi/pico-micropython-examples/tree/master/pio/neopixel_ring) example, stand more chance of inclusion.