[DOC] Add web ufs preview in the accelerating web ufs demo

[TrafalgarZZZ]

Provide a link to that doc page: https://github.com/fluid-cloudnative/fluid/blob/master/docs/zh/samples/accelerate_data_accessing.md

What is the defect and your suggestions on improvement: Apache mirror site used in the demo doc (e.g. https://mirrors.tuna.tsinghua.edu.cn/apache/hbase/stable/) may change over time. Following the instructions in the demo doc step by step, users might be confused about why the demo can't work as expected.

My suggestion is to add a quick preview (for example, a screenshot of the mirror site) in the demo doc to let users know what's the web ufs should be like. When the web site is not available, the demo doc also should provide some backup plans(for example, links to other mirror site) to users.