fix: core/readme/package.json to reduce vulnerabilities (#216)

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-DOMPURIFY-474012

Author: snyk-bot

core/readme/package.json

@@ -30,7 +30,7 @@
     "lib"
   ],
   "dependencies": {
-    "dompurify": "2.0.6",
+    "dompurify": "2.0.7",
     "jsdom": "15.2.0",
     "marked": "0.7.0"
   },