docs: add create meeting timepicker demo doc

components/meetingTimePicker/doc.txt

+<------------------axml------------------>
+<button size="default" type="primary" onTap="showPop">Button</button>
+
+<popup 
+  show="{{show}}"
+  onClose="closePop"
+  title="请选择会议时间"
+>
+<meeting-time-picker
+    onClose="closePop"
+    onComplete="Complete"
+    visibleItemCount="3"
+    startTime="{{startTime}}"
+    endTime="{{endTime}}"
+ ></meeting-time-picker>
+</popup>
+
+<------------------js------------------>
+Page({
+  data: {
+    show:false,
+    startTime: new Date()
+  },
+  showPop(){
+    this.setData({
+      show: true
+    })
+  },
+  closePop(){
+    this.setData({
+      show: false
+    })
+  },
+  Complete(data){
+    console.log(data)
+    this.closePop();
+  }
+});
+
+<------------------json------------------>
+{
+    "usingComponents": {
+        "popup": "../../components/popup/index",
+        "meeting-time-picker": "../../components/meetingTimePicker/meetingTimePicker"
+    }
+}
\ No newline at end of file