Update README.md

Author: sochs

README.md

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 ESP8582 based WLAN Thermometer
 
+Functional Description: https://github.com/WLANThermo-nano/WLANThermo_nano_Software/wiki
+
 This works with the ESP8266 Arduino platform with a recent stable release(2.0.0 or newer) 
 https://github.com/esp8266/Arduino and the Arduino Time Library https://github.com/PaulStoffregen/Time.