Add M.A.R.S. Rover (#5407)

Author: martinwork

Diff for: docs/extensions.md

@@ -505,6 +505,10 @@ Check out [the accessories pages on microbit.org](https://microbit.org/buy/acces
 
 ```codecard
 [{
+  "name": "4tronix M.A.R.S. Rover",
+  "url":"/pkg/4tronix/mars-rover",
+  "cardType": "package"
+}, {
   "name": "Cytron MOTION:BIT",
   "url":"/pkg/CytronTechnologies/pxt-motionbit",
   "cardType": "package"

Diff for: targetconfig.json

@@ -452,7 +452,8 @@
             "elecfreaks/pxt-cutebot-pro": { "tags": [ "Robotics" ], "preferred": true },
             "microbit-foundation/makecode-tutorials": {},
             "grandpabond/pxt-meter": { "tags": [ "Software" ] },
-            "microsoft/microbit-robot": { "tags": [ "Robotics" ] }
+            "microsoft/microbit-robot": { "tags": [ "Robotics" ] },
+            "4tronix/mars-rover": { "tags": [ "Robotics" ] }
         },
         "upgrades": {
             "tinkertanker/pxt-iot-environment-kit": "min:v4.2.1",