docs: add service doc for azdfs

[dqhl76]

Update #2304

[Xuanwo]

Thanks a lot!

[dqhl76]

May be we also need to add use opendal::Scheme; for this https://github.com/apache/incubator-opendal/blob/a189eef962c8e2a30a371845d4aa0499c5c24803/website/docs/services/azblob.mdx?plain=1#L35
I will add it next time

[Xuanwo]

May be we also need to add use opendal::Scheme; for this

https://github.com/apache/incubator-opendal/blob/a189eef962c8e2a30a371845d4aa0499c5c24803/website/docs/services/azblob.mdx?plain=1#L35

Yes, and we can remove use opendal::services::Azdfs.