Add button to remove a tag

CHDataManagement/Main/SelectedContent.swift

@@ -29,6 +29,12 @@ final class SelectedContent: ObservableObject {
         }
     }
 
+    func remove(_ tag: Tag) {
+        if self.tag == tag {
+            self.tag = nil
+        }
+    }
+
     func remove(_ file: FileResource) {
         if self.file == file {
             self.file = nil