docs: remove legacy slot usage

src/form/demo/FieldTypeArea.vue

@@ -8,19 +8,20 @@
     :placeholder="t('placeholder')"
     @click="showArea = true"
   >
-    <van-popup
-      v-model="showArea"
-      round
-      slot="extra"
-      position="bottom"
-      get-container="body"
-    >
-      <van-area
-        :area-list="t('areaList')"
-        @confirm="onConfirm"
-        @cancel="onCancel"
-      />
-    </van-popup>
+    <template #extra>
+      <van-popup
+        v-model="showArea"
+        round
+        position="bottom"
+        get-container="body"
+      >
+        <van-area
+          :area-list="t('areaList')"
+          @confirm="onConfirm"
+          @cancel="onCancel"
+        />
+      </van-popup>
+    </template>
   </van-field>
 </template>
 

src/form/demo/FieldTypeCalendar.vue

@@ -8,13 +8,14 @@
     :placeholder="t('placeholder')"
     @click="showCalendar = true"
   >
-    <van-calendar
-      v-model="showCalendar"
-      round
-      slot="extra"
-      get-container="body"
-      @confirm="onConfirm"
-    />
+    <template #extra>
+      <van-calendar
+        v-model="showCalendar"
+        round
+        get-container="body"
+        @confirm="onConfirm"
+      />
+    </template>
   </van-field>
 </template>
 

src/form/demo/FieldTypeDatetimePicker.vue

@@ -8,19 +8,20 @@
     :placeholder="t('placeholder')"
     @click="showPicker = true"
   >
-    <van-popup
-      v-model="showPicker"
-      round
-      slot="extra"
-      position="bottom"
-      get-container="body"
-    >
-      <van-datetime-picker
-        type="time"
-        @confirm="onConfirm"
-        @cancel="onCancel"
-      />
-    </van-popup>
+    <template #extra>
+      <van-popup
+        v-model="showPicker"
+        round
+        position="bottom"
+        get-container="body"
+      >
+        <van-datetime-picker
+          type="time"
+          @confirm="onConfirm"
+          @cancel="onCancel"
+        />
+      </van-popup>
+    </template>
   </van-field>
 </template>
 

src/form/demo/FieldTypePicker.vue

@@ -8,20 +8,21 @@
     :placeholder="t('placeholder')"
     @click="showPicker = true"
   >
-    <van-popup
-      v-model="showPicker"
-      round
-      slot="extra"
-      position="bottom"
-      get-container="body"
-    >
-      <van-picker
-        show-toolbar
-        :columns="t('textColumns')"
-        @confirm="onConfirm"
-        @cancel="onCancel"
-      />
-    </van-popup>
+    <template #extra>
+      <van-popup
+        v-model="showPicker"
+        round
+        position="bottom"
+        get-container="body"
+      >
+        <van-picker
+          show-toolbar
+          :columns="t('textColumns')"
+          @confirm="onConfirm"
+          @cancel="onCancel"
+        />
+      </van-popup>
+    </template>
   </van-field>
 </template>