add Kitronik zip tile (#1816)

* add Kitronik zip tile

* fixing link

docs/extensions.md

@@ -333,6 +333,10 @@ Check out [microbit.org](http://microbit.org/resellers/) for more information on
   "name": "51bit ColorBit",
   "url":"/pkg/51bit/ColorBit",
   "cardType": "package"
+}, {
+  "name": "Kitronik Zip Tile",
+  "url":"/pkg/KitronikLtd/pxt-kitronik-zip-tile",
+  "cardType": "package"
 }, {
   "name": "MAX7219 8x8",
   "url":"/pkg/alankrantas/pxt-MAX7219_8x8",