add optionalChaining

Update use-weex.md

修复一个文档错误，导致页面中没显示该内容https://uniapp.dcloud.io/use-weex?id=nvue%e5%bc%80%e5%8f%91%e4%b8%8evue%e5%bc%80%e5%8f%91%e7%9a%84%e5%b8%b8%e8%a7%81%e5%8c%ba%e5%88%ab

Update navigationbar.md