Add missing Massachusetts country code (#3562)

Massachusetts has a flag SVG, but does not appear in the selection
because it's missing from the countries.json.

## Description:

Add Massachusetts to countries.json

resources/countries.json

@@ -1231,6 +1231,11 @@
     "continent": "North America",
     "name": "Maine"
   },
+  {
+    "code": "Massachusetts",
+    "continent": "North America",
+    "name": "Massachusetts"
+  },
   {
     "code": "mw",
     "continent": "Africa",