Add the AppVeyor badge

Author: brettcannon

package.json

@@ -20,7 +20,12 @@
         {
             "url": "https://travis-ci.org/Microsoft/vscode-python.svg?branch=master",
             "href": "https://travis-ci.org/Microsoft/vscode-python",
-            "description": "Continuous integration"
+            "description": "Continuous integration (Travis)"
+        },
+        {
+            url: "https://ci.appveyor.com/api/projects/status/s0pt8d79gqw222j7?svg=true",
+            "href: "https://ci.appveyor.com/project/DonJayamanne/vscode-python-v3vd6/branch/master",
+            "description": "Continuous integration (AppVeyor)"
         },
         {
             "url": "https://codecov.io/gh/Microsoft/vscode-python/branch/master/graph/badge.svg",
@@ -1871,4 +1876,4 @@
         "publisherDisplayName": "Microsoft",
         "publisherId": "998b010b-e2af-44a5-a6cd-0b5fd3b9b6f8"
     }
-}
+}