chore(package): update markdownlint-cli to version 0.18.0

Author: greenkeeper[bot]

package.json

@@ -65,7 +65,7 @@
     "good-squeeze": "5.1.0",
     "hapi": "^18.1.0",
     "husky": "^3.0.1",
-    "markdownlint-cli": "^0.17.0",
+    "markdownlint-cli": "^0.18.0",
     "material-ui": "0.20.2",
     "mocha": "^6.2.0",
     "mustache": "^3.0.1",