fix(package): update ngx-markdown to version 9.0.0

Closes #21

Author: greenkeeper[bot]

demo/package.json

@@ -34,7 +34,7 @@
     "core-js": "^3.1.1",
     "font-awesome": "^4.7.0",
     "hammerjs": "^2.0.8",
-    "ngx-markdown": "^7.1.5",
+    "ngx-markdown": "^9.0.0",
     "rxjs": "^6.5.2",
     "zone.js": "^0.8.26"
   },