Improve header handling for post lists

CHDataManagement/Generator/Results/PageGenerationResults.swift

@@ -242,6 +242,10 @@ final class PageGenerationResults: ObservableObject {
         onMain { self.requiredHeaders.formUnion(headers) }
     }
 
+    func require<S>(headers: S) where S: Sequence, S.Element == KnownHeaderElement {
+        onMain { self.requiredHeaders.formUnion(headers) }
+    }
+
     func require(icon: PageIcon) {
         onMain { self.requiredIcons.insert(icon) }
     }