I have embedded some URLs in some OpenRoads Item Types.
There's a bit of a philosophical conflict here.
If Item Types are an attempt to bring external data intrinsic to a feature, then linking out to another source can lead to a bias towards keeping everything in an external source.
But some information really does need to remain external.
Many designers and managers are getting in the habit of sharing information better via shareable documents or containers - OpenNote, Sharepoint Sites, webs, etc. This is a good trend.
I was reluctant to create a Property specifically for an External link, for fear of making it to easy to default to "external data" when the information might better be internal. An advantage of a separate field for an External reference is that that field can be checked for being non-empty vs. trying to pattern match to flag it for a View Display Rule,
The QC_Link View Display Rule I used searched multiple fields for "http" only. This not only is not a robust check, it is dramatically slower than a non-empty check.