fix(package): update stylelint to version 13.1.0

Closes #2

Author: greenkeeper[bot]

package.json

@@ -22,7 +22,7 @@
     "node-wit": "^5.0.0",
     "probot": "^7.4.0",
     "probot-scheduler": "^1.2.0",
-    "stylelint": "^9.9.0",
+    "stylelint": "^13.1.0",
     "stylelint-config-recommended": "^2.1.0",
     "stylelint-config-standard": "^18.2.0",
     "uuid": "^3.3.2"