Update asyncio_simpletest.py

Simple copy/paste beginning from 

https://learn.adafruit.com/cooperative-multitasking-in-circuitpython-with-asyncio/concurrent-tasks#one-led-3106269

to correct an issue raised, of all places, in the Issues section.

Author: johnnohj

examples/asyncio_simpletest.py

@@ -1,4 +1,57 @@
-# SPDX-FileCopyrightText: 2017 Scott Shawcroft, written for Adafruit Industries
-# SPDX-FileCopyrightText: Copyright (c) 2021 Dan Halbert for Adafruit Industries
+# SPDX-FileCopyrightText: 2022 Dan Halbert for Adafruit Industries
 #
-# SPDX-License-Identifier: Unlicense
+# SPDX-License-Identifier: MIT
+
+### Example for one led:
+
+import asyncio
+import board
+import digitalio
+
+
+async def blink(pin, interval, count):  # Don't forget the async!
+    with digitalio.DigitalInOut(pin) as led:
+        led.switch_to_output(value=False)
+        for _ in range(count):
+            led.value = True
+            await asyncio.sleep(interval)  # Don't forget the await!
+            led.value = False
+            await asyncio.sleep(interval)  # Don't forget the await!
+
+
+async def main():  # Don't forget the async!
+    led_task = asyncio.create_task(blink(board.D1, 0.25, 10))
+    await asyncio.gather(led_task)  # Don't forget the await!
+    print("done")
+
+
+asyncio.run(main())
+
+
+### Example for two leds:
+
+import asyncio
+import board
+import digitalio
+
+
+async def blink(pin, interval, count):
+    with digitalio.DigitalInOut(pin) as led:
+        led.switch_to_output(value=False)
+        for _ in range(count):
+            led.value = True
+            await asyncio.sleep(interval)  # Don't forget the "await"!
+            led.value = False
+            await asyncio.sleep(interval)  # Don't forget the "await"!
+
+
+async def main():
+    led1_task = asyncio.create_task(blink(board.D1, 0.25, 10))
+    led2_task = asyncio.create_task(blink(board.D2, 0.1, 20))
+
+    await asyncio.gather(led1_task, led2_task)  # Don't forget "await"!
+    print("done")
+
+
+asyncio.run(main())
+