add the Extra field back to cloze deletions as "Back Extra"

Originally removed because some users were adding cloze deletions to
it, but removing it just replaced that problem with a new problem where
users add the field but don't add it to their card templates.

rslib/ftl/notetypes.ftl

@@ -4,6 +4,7 @@ notetypes-front-field = Front
 notetypes-back-field = Back
 notetypes-add-reverse-field = Add Reverse
 notetypes-text-field = Text
+notetypes-back-extra-field = Back Extra
 
 ## Default note type names
 

rslib/src/findreplace.rs

@@ -142,11 +142,16 @@ mod test {
         assert_eq!(&note.fields, &["one BBB", "two BBB"]);
 
         let note2 = col.storage.get_note(note2.id)?.unwrap();
-        assert_eq!(&note2.fields, &["three BBB"]);
+        assert_eq!(&note2.fields, &["three BBB", ""]);
 
         assert_eq!(
             col.storage.field_names_for_notes(&nids)?,
-            vec!["Back".to_string(), "Front".into(), "Text".into()]
+            vec![
+                "Back".to_string(),
+                "Back Extra".into(),
+                "Front".into(),
+                "Text".into()
+            ]
         );
         let cnt = col.find_and_replace(nids.clone(), "BBB", "ccc", Some("Front".into()))?;
         // still 2, as the caller is expected to provide only note ids that have

rslib/src/notetype/stock.rs

@@ -112,8 +112,11 @@ pub(crate) fn cloze(i18n: &I18n) -> NoteType {
     nt.name = i18n.tr(TR::NotetypesClozeName).into();
     let text = i18n.tr(TR::NotetypesTextField);
     nt.add_field(text.as_ref());
-    let fmt = format!("{{{{cloze:{}}}}}", text);
-    nt.add_template(nt.name.clone(), fmt.clone(), fmt);
+    let back_extra = i18n.tr(TR::NotetypesBackExtraField);
+    nt.add_field(back_extra.as_ref());
+    let qfmt = format!("{{{{cloze:{}}}}}", text);
+    let afmt = format!("{}<br>\n{{{{{}}}}}", qfmt, back_extra);
+    nt.add_template(nt.name.clone(), qfmt, afmt);
     nt.config.kind = NoteTypeKind::Cloze as i32;
     nt.config.css += "
 .cloze {