Add a Chinese version Documentation & Fix bug while building website.

[marcuswang6]

What I've Done

1. replace ./docs/themes/iceberg-theme with ./iceberg-theme to debug Error: readdir D:\iceberg-docs\docs\themes\iceberg-theme\: The directory name is invalid.
2. copy the English ./docs/content to ./docs/content.zh to generate original Chinese version documentation.
3. revise config.toml to add an entrance of Chinese Doc at the sidebar.

Preview

[bitsondatadev]

@Waterkin, would you mind moving this over to https://github.com/apache/iceberg/pulls please? This repository is being moved to the main repository.