feat(Rate): 当使用 readonly 和 allow-half 时支持 modelValue 设置小数 (#8528)

* feat(Rate): 当使用readonly和allow-half时支持modelValue设置小数

* docs(Rate): 完善文档

* docs(Rate): update snapshot

* docs(Rate): add description of decimal value

Co-authored-by: neverland <chenjiahan@buaa.edu.cn>

src/rate/README.md

@@ -88,6 +88,23 @@ export default {
 <van-rate v-model="value" readonly />
 ```
 
+### Readonly Half Star
+
+```html
+<van-rate v-model="value" readonly />
+```
+
+```js
+import { ref } from 'vue';
+
+export default {
+  setup() {
+    const value = ref(3.3);
+    return { value };
+  },
+};
+```
+
 ### Change Event
 
 ```html