Timeline mode支持左右同时显示风格

[fifsky]

• I have searched the issues of this repository and believe that this is not a duplicate.

What problem does this feature solve?

当前的timeline mode支持 left right和左右轮替显示alternate，是否可以添加一个选项，支持在同一行左右都可以显示内容，比如左边显示时间，右边显示事件内容，比如：

2015-09-01  O  Create a services site  
            |
2015-09-01  O  Solve initial network problems 
            |
2015-09-01  O  Technical testing

What does the proposed API look like?

<Timeline>
    <Timeline.Item lable="2015-09-01">Create a services site</Timeline.Item>
    <Timeline.Item lable="2015-09-01">Solve initial network problems</Timeline.Item>
    <Timeline.Item lable="2015-09-01">Technical testing</Timeline.Item>
</Timeline>

[MrHeer]

May be I can try it

[MrHeer]

Need to add a new mode?

[xrkffgg]

see #18032 😏

[xrkffgg]

还有点问题。。。有点不太对，我再改改

[kerm1it]

I will work it.