Restore DistributedLog website

[nicoloboschi]

BUG REPORT

Describe the bug

DistributedLog website is not available at: https://bookkeeper.apache.org/distributedlog/docs/latest/user_guide/api/core I'm not sure the cause is the new website. The docs is in his old repository: https://github.com/apache/distributedlog/tree/master/website

Probably it happened when we switched to the ASF infra deployment

[nicoloboschi]

Probably the quickest path is to move the markdown files into the bookkeeper repository.

[hezhangjian]

@nicoloboschi Where is the initial DistributedLog website? I can help with this.