feat: add llm Select to KeywordExtractForm #918 (#1492)

### What problem does this PR solve?

feat: add llm Select to KeywordExtractForm #918

### Type of change


- [x] New Feature (non-breaking change which adds functionality)

web/src/components/top-n-item.tsx

@@ -5,14 +5,18 @@ type FieldType = {
   top_n?: number;
 };
 
-const TopNItem = () => {
+interface IProps {
+  initialValue?: number;
+}
+
+const TopNItem = ({ initialValue = 8 }: IProps) => {
   const { t } = useTranslate('chat');
 
   return (
     <Form.Item<FieldType>
       label={t('topN')}
       name={'top_n'}
-      initialValue={8}
+      initialValue={initialValue}
       tooltip={t('topNTip')}
     >
       <Slider max={30} />