Added package for PCA9685 micro:bit-support:4139 (#611)

docs/packages.md

@@ -83,5 +83,9 @@
   "name": "Katakana",
   "url":"/pkg/mbitfun/pxt-katakana",
   "cardType": "package"
+  }, {
+  "name": "PCA9685 LED controller",
+  "url":"/pkg/jdarling/pxt-pca9685",
+  "cardType": "package"
 }]
 ```

targetconfig.json

@@ -16,7 +16,8 @@
             "sparkfun/pxt-weather-bit",
             "minodekit/pxt-minode",
             "LaboratoryForPlayfulComputation/pxt-blockytalkyBLE",
-            "mbitfun/pxt-katakana"
+            "mbitfun/pxt-katakana",
+            "jdarling/pxt-pca9685"
         ],
         "preferredRepos": [
             "Microsoft/pxt-neopixel"