chore(package): update markdown-it to version 9.0.1

Closes #19

Author: greenkeeper[bot]

package.json

@@ -11,7 +11,7 @@
     "url": "[email protected]:revin/markdown-it-expand-tabs.git"
   },
   "devDependencies": {
-    "markdown-it": "^8.0.1",
+    "markdown-it": "^9.0.1",
     "mocha": "^5.0.3"
   },
   "keywords": [