Type Extensions do not render if the target object is a CustomDocument

[sbendfelt]

PurchaseOrder__Rank-10.xml
DocumentPouchC1__Rank-100.xml

Issue is with the Interpreter Regex:
/[a-zA-Z-_]+__Rank-\d+\.xml$/

should be:
/[a-zA-z-_0-9]+__Rank-\d+\.xml$/