fix(package): update ngx-highlightjs to version 2.1.3

Closes #45

Author: greenkeeper[bot]

demo/package.json

@@ -47,7 +47,7 @@
     "include-media": "^1.4.9",
     "material-design-icons": "^3.0.1",
     "ngx-clipboard": "^11.1.9",
-    "ngx-highlightjs": "2.1.1",
+    "ngx-highlightjs": "2.1.3",
     "ngx-markdown": "^7.0.0",
     "ngx-material-pages": "^1.3.2",
     "rxjs": "^6.3.3",