use isolation characters instead of direction markers in cloze handling

https://anki.tenderapp.com/discussions/ankidesktop/40443-improper-location-of-c1foo-on-ltr-text-in-an-rtl-cloze-field

qt/ts/src/editor.ts

@@ -295,8 +295,8 @@ function wrapIntoText(front, back) {
 
 function wrapInternal(front, back, plainText) {
     if (currentField.dir === "rtl") {
-        front = "‫" + front + "‬";
-        back = "‫" + back + "‬";
+        front = "⁨" + front + "⁩";
+        back = "⁨" + back + "⁩";
     }
     const s = window.getSelection();
     let r = s.getRangeAt(0);