fix(package): update ngx-highlightjs to version 4.0.0

Closes #45

Author: greenkeeper[bot]

demo/package.json

@@ -48,7 +48,7 @@
     "include-media": "^1.4.9",
     "material-design-icons": "^3.0.1",
     "ngx-clipboard": "^11.1.9",
-    "ngx-highlightjs": "2.1.1",
+    "ngx-highlightjs": "4.0.0",
     "ngx-markdown": "^7.1.4",
     "ngx-material-pages": "^1.3.2",
     "rxjs": "^6.4.0",