Improve English Documentation

Hi, your commit to #56 is great.

However, after careful rereading, I found several more typos and grammatical errors. Also, compared with the Chinese documentation, there exist some mechanical translations in the English version. These problems are fixed in these commits.

With mostly grammar corrections, the information from the documentation is NOT changed.

In the Settings section, I added some more information to `data` and re-paragraphed the information in `data` and `search_key` for better clarify and logic.

Tell me if I made any technical mistake.