Add electron-windows-store dev dependency

Author: kevinsawicki

package.json

@@ -41,6 +41,7 @@
     "devtron": "^1.0.0",
     "electron-packager": "^7.0.1",
     "electron-prebuilt": "~1.0.2",
+    "electron-windows-store": "^0.2.7",
     "electron-winstaller": "^2.2.0",
     "mocha": "^2.3.4",
     "request": "^2.70.0",