Extension: add Petal:bit (#6312)

Co-authored-by: Abhijith Chatra <[email protected]>

Author: martinwork

docs/extensions/extension-gallery.md

@@ -867,6 +867,10 @@ Many extensions are available to work with interface kits, add-on hardware, or o
 
 ```codecard
 [{
+    "name": "Elecfreaks Petal:bit",
+    "url": "/pkg/elecfreaks/pxt-petal",
+    "cardType": "package"
+}, {
     "name": "Joy IT RFID Module MFRC-522",
     "url": "/pkg/joy-it/pxt-rfid-mfrc522",
     "cardType": "package"

targetconfig.json

@@ -476,6 +476,7 @@
             "ines-hpmm/pxt-luma-matrix": { "tags": [ "Lights and Display" ] },
             "team-bp/pxt-bplab": { "tags": [ "Science" ] },
             "jimd80/pxt-coderdojo-controller": { "tags": [ "Gaming" ] },
+            "elecfreaks/pxt-petal": { "tags": [ "Science" ] },
             "microsoft/pxt-simx-sample": {
                 "simx": {
                     "sha": "7301f5900879b85127482d79bab48f03c25690a8",