docs: add English User Guide.

[fenghlin666]

PR

PR Checklist

Please check if your PR fulfills the following requirements:

• [ ] The commit message follows our Commit Message Guidelines
• [ ] Tests for the changes have been added (for bug fixes / features)
• [x] Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• [ ] Bugfix
• [ ] Feature
• [ ] Code style update (formatting, local variables)
• [ ] Refactoring (no functional changes, no api changes)
• [ ] Build related changes
• [ ] CI related changes
• [x] Documentation content changes
• [ ] Other... Please describe:

What is the current behavior?

Issue Number: N/A

What is the new behavior?

Does this PR introduce a breaking change?

• [ ] Yes
• [x] No

Other information