adding the BH1750 from their downloads

BH1750/examples/BH1750onetime/BH1750onetime.ino

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+/*
+
+  Example of BH1750 library usage.
+
+  This example initialises the BH1750 object using the high resolution
+  one-time mode and then makes a light level reading every second.
+
+  The BH1750 component starts up in default mode when it next powers up.
+  The BH1750 library automatically reconfigures the one-time mode in
+  preparation for the next measurement.
+
+*/
+
+#include <Wire.h>
+#include <BH1750.h>
+
+BH1750 lightMeter;
+
+void setup(){
+
+  Serial.begin(9600);
+
+  // Initialize the I2C bus (BH1750 library doesn't do this automatically)
+  Wire.begin();
+  // On esp8266 you can select SCL and SDA pins using Wire.begin(D4, D3);
+
+  lightMeter.begin(BH1750::ONE_TIME_HIGH_RES_MODE);
+
+  Serial.println(F("BH1750 One-Time Test"));
+
+}
+
+
+void loop() {
+
+  while (!lightMeter.measurementReady(true)) {
+    yield();
+  }
+  float lux = lightMeter.readLightLevel();
+  Serial.print("Light: ");
+  Serial.print(lux);
+  Serial.println(" lx");
+  lightMeter.configure(BH1750::ONE_TIME_HIGH_RES_MODE);
+}