Fill the emptiness of generated doc

[weihanglo]

The generated Rust doc is public now. Yet it seems too dumb and lack some descriptions. The crate and each modules need to be documented.

For crate doc itself, suppose we can reuse the English version of the root README.md file. Concerning module level docs, the Chinese articles are also absent. We should write down both English and Chinese intros for these three modules.

Any thought Rustaceans?

Missing Docs

• crate itself
• searching module
• collections module
• sorting module