I believe the official documentation you've linked to is missing another item in the intent parts type
.
The intent you want to call in Java would be:
Intent intent = new Intent(ContactsContract.Intents.Insert.ACTION);
intent.setType(ContactsContract.Contacts.CONTENT_TYPE);
If we translate the constants to literals, that would be:
Intent intent = new Intent("android.intent.action.INSERT");
intent.setType("vnd.android.cursor.dir/contact");
If we now translate that to chrome's Android intent scheme, that would be:
var url = "intent:#Intent;action=android.intent.action.INSERT;type=vnd.android.cursor.dir/contact;end"
Note that you must have a user interaction in order for Chrome on Android to call this intent, so it needs to be in a button or similar to make it work (typing directly to the address bar will not work as well)