Updated library to work with ESP8266 board manager version 3.0.0

examples/SHT_SIMPLE/SHT_SIMPLE.ino

@@ -1,3 +1,21 @@
+/*
+This is the code for the AirGradient DIY Air Quality Sensor with an ESP8266 Microcontroller.
+
+It is a high quality sensor showing PM2.5, CO2, Temperature and Humidity on a small display and can send data over Wifi.
+
+For build instructions please visit https://www.airgradient.com/diy/
+
+Compatible with the following sensors:
+SHT30/31 (Temperature/Humidity Sensor)
+
+Please install ESP8266 board manager (tested with version 3.0.0)
+
+If you are a school or university contact us for a free trial on the AirGradient platform.
+https://www.airgradient.com/schools/
+
+MIT License
+*/
+
 #include <AirGradient.h>
 AirGradient ag = AirGradient();