fix: package.json to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-MARKED-174116

Author: snyk-bot

package.json

@@ -33,6 +33,6 @@
     "codemirror": "^5.6.0",
     "codemirror-graphql": "^0.1.1",
     "graphql": "^0.4.3",
-    "marked": "^0.3.5"
+    "marked": "^0.6.2"
   }
 }