Merge pull request #284 from adafruit/ltr390

adding ltr390

Author: jepler

.gitmodules

@@ -760,3 +760,6 @@
 [submodule "libraries/drivers/scd30"]
 	path = libraries/drivers/scd30
 	url = https://github.com/adafruit/Adafruit_CircuitPython_SCD30.git
+[submodule "libraries/drivers/ltr390"]
+	path = libraries/drivers/ltr390
+	url = https://github.com/adafruit/Adafruit_CircuitPython_LTR390.git

docs/drivers.rst

@@ -384,6 +384,7 @@ These sensors detect light related attributes such as ``color``, ``light`` (unit
     AS726x Color Spectrum Sensor <https://circuitpython.readthedocs.io/projects/as726x/en/latest/>
     AS7341 11-Channel Multi-Spectral Digital Sensor <https://circuitpython.readthedocs.io/projects/as7341/en/latest/>
     BH1750 Ambient Light <https://circuitpython.readthedocs.io/projects/bh1750/en/latest/>
+    LTR390 Ambient Light and UV Sensor <https://circuitpython.readthedocs.io/projects/ltr390/en/latest/>
     TCS34725 Color Sensor <https://circuitpython.readthedocs.io/projects/tcs34725/en/latest/>
     TSL2561 Light Sensor <https://circuitpython.readthedocs.io/projects/tsl2561/en/latest/>
     TSL2591 High Dynamic Range Light Sensor <https://circuitpython.readthedocs.io/projects/tsl2591/en/latest/>