[Doc] rename component README file (#3662)

src/panel/README.md

@@ -0,0 +1,50 @@
+# Panel
+
+### Install
+
+``` javascript
+import { Panel } from 'vant';
+
+Vue.use(Panel);
+```
+
+## Usage
+
+### Basic Usage
+
+```html
+<van-panel title="Title" desc="Description" status="Status">
+  <div>Content</div>
+</van-panel>
+```
+
+### Advanced Usage
+
+```html
+<van-panel title="Title" desc="Description" status="Status">
+  <div>Content</div>
+  <div slot="footer">
+    <van-button size="small">Button</van-button>
+    <van-button size="small" type="danger">Button</van-button>
+  </div>
+</van-panel>
+```
+
+## API
+
+### Props
+
+| Attribute | Description | Type | Default |
+|------|------|------|------|
+| icon | Left Icon | `String` | - |
+| title | Title | `String` | - |
+| desc | Description | `String` | - |
+| status | Status | `String` | - |
+
+### Slots
+
+| Name | Description |
+|------|------|
+| default | Default slot |
+| header | Custom header |
+| footer | Custom footer |