add kitronik access bit (#1854)

* add kitronik access bit

* Update targetconfig.json

* Update extensions.md

docs/extensions.md

@@ -87,6 +87,10 @@ Check out [microbit.org](http://microbit.org/resellers/) for more information on
   "name": "Inex iKB-1 controller board",
   "url":"/pkg/jcubuntu/pxt-iKB1",
   "cardType": "package"
+}, {
+  "name": "Kitronik ACCESS:bit",
+  "url":"/pkg/KitronikLtd/pxt-kitronik-accessbit",
+  "cardType": "package"
 }]
 ```