adding picowbell doubler battery examples

PiCowbell_Doubler/CircuitPython_PiCowbell_Doubler_Battery_Monitor/code.py

@@ -0,0 +1,22 @@
+# SPDX-FileCopyrightText: 2024 ladyada for Adafruit Industries
+#
+# SPDX-License-Identifier: MIT
+
+import time
+import board
+from analogio import AnalogIn
+from digitalio import DigitalInOut, Direction
+
+led = DigitalInOut(board.LED)
+led.direction = Direction.OUTPUT
+
+analog_in = AnalogIn(board.A3)
+
+def get_vsys(pin):
+    return ((pin.value * 3) * 3.3) / 65536
+
+while True:
+    led.value = True
+    print(f"The battery level is: {get_vsys(analog_in):.1f}V")
+    led.value = False
+    time.sleep(5)