在h5中使用navigator组件问题

**问题描述**

1. 在h5中使用navigator组件，open-type为"navigateBack"，此时将delta设置为1时会报：Expected Number with value 1, got String with value "1".

2. 触发该组件报：<navigator/> should have url attribute when using navigateTo, redirectTo, reLaunch or switchTab



<navigator  open-type="navigateBack" :delta="1"  hover-class="none"></navigator>

**预期结果**

希望navigator增加对navigateBack的支持
