Add back button to QuizRunner component

client/src/components/QuizRunner.tsx

@@ -487,6 +487,9 @@ export default function QuizRunner({ defaultMode = 'all', defaultEntryId, autoSt
         )}
         {showResult && (
           <>
+            <button className="button button--ghost" onClick={goPrev} disabled={currentIndex === 0}>
+              Back
+            </button>
             <button className="button button--primary" onClick={goNext}>
               {currentIndex + 1 === questions.length ? 'Finish' : 'Next'}
             </button>