Added HTU21 Sensor (#588)

* Added HTU21 Sensor Support

Co-authored-by: Jonathan Wells <jonathan-wells@oist.jp>

platformio.ini

@@ -80,6 +80,7 @@ unifiedsensor = Adafruit Unified Sensor@1.0.2
 tsl2561 = Adafruit TSL2561@1.0.3
 bme280 = SparkFun BME280@2.0.4
 bmp180 = BMP180@efac46bd8d
+htu21 = SparkFun HTU21D Humidity and Temperature Sensor Br@1.1.3
 ina226 = jarzebski/Arduino-INA226#968a684
 a6lib = 1technophile/A6lib
 wifimanager = tzapu/WiFiManager#c3ff582
@@ -173,6 +174,7 @@ lib_deps =
   ${libraries.newremoteswitch}
   ${libraries.bme280}
   ${libraries.bmp180}
+  ${libraries.htu21}
   ${libraries.unifiedsensor}
   ${libraries.dht}
   ${libraries.tsl2561}
@@ -194,6 +196,7 @@ build_flags =
   '-DZsensorADC="ADC"'
   '-DZsensorBH1750="BH1750"'
   '-DZsensorBME280="BME280"'
+  '-DZsensorHTU21="HTU21"'
   '-DZsensorTSL2561="TSL2561"'
   '-DZsensorDHT="DHT"'
   '-DZsensorDS1820="DS1820"'
@@ -361,6 +364,7 @@ lib_deps =
   ${libraries.newremoteswitch}
   ${libraries.bme280}
   ${libraries.bmp180}
+  ${libraries.htu21}
   ${libraries.unifiedsensor}
   ${libraries.dht}
   ${libraries.tsl2561}
@@ -386,6 +390,7 @@ build_flags =
   '-DZsensorADC="ADC"'
   '-DZsensorBH1750="BH1750"'
   '-DZsensorBME280="BME280"'
+  '-DZsensorHTU21="HTU21"'
   '-DZsensorTSL2561="TSL2561"'
   '-DZsensorDHT="DHT"'
   '-DZsensorDS1820="DS1820"'
@@ -576,6 +581,7 @@ lib_deps =
   ${libraries.newremoteswitch}
   ${libraries.bme280}
   ${libraries.bmp180}
+  ${libraries.htu21}
   ${libraries.unifiedsensor}
   ${libraries.dht}
   ${libraries.tsl2561}
@@ -598,6 +604,7 @@ build_flags =
   '-DZsensorADC="ADC"'
   '-DZsensorBH1750="BH1750"'
   '-DZsensorBME280="BME280"'
+  '-DZsensorHTU21="HTU21"'
   '-DZsensorTSL2561="TSL2561"'
   '-DZsensorDHT="DHT"'
   '-DZsensorDS1820="DS1820"'