add gcube (#5632)

docs/extensions/extension-gallery.md

@@ -517,6 +517,10 @@ Many extensions are available to work with interface kits, add-on hardware, or o
 
 ```codecard
 [{
+  "name": "Gcube",
+  "url":"/pkg/roborisen/gcube",
+  "cardType": "package"
+}, {
   "name": "Roversa",
   "url":"/pkg/eb8ga/pxt-roversa-2",
   "cardType": "package"

targetconfig.json

@@ -459,7 +459,8 @@
             "grandpabond/pxt-flexfx": { "tags": [ "Software" ] },
             "grandpabond/pxt-faces": { "tags": [ "Software" ] },
             "joylabz/code-a-key-extension": {},
-            "eb8ga/pxt-roversa-2": { "tags": [ "Robotics" ] }
+            "eb8ga/pxt-roversa-2": { "tags": [ "Robotics" ] },
+            "roborisen/gcube": { "tags": [ "Robotics" ] }
         },
         "upgrades": {
             "tinkertanker/pxt-iot-environment-kit": "min:v4.2.1",