Added README and image preview of the AQI monitor.

README.md

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+# Description
+
+A simple AQI monitor made using Arduino Nano and Sen44 sensor.
+
+![AQI Monitor](aqi_monitor.webp)
+
+Sen44 was found in Amazon's AQI monitor. Note, Sensirion has discontinued Sen44 and 
+has replaced them with new Sen5(0,4,5) models.
+
+Appropriate documentation and libraries can be found on their [website](https://sensirion.com/).
+
+* [Sen44 Arduino Library](https://github.com/Sensirion/arduino-i2c-sen44)
+* [Arduino Nano](https://store.arduino.cc/products/arduino-nano)