docs(plugin-baidu-analytics): improve baidu analytics docs about SPA mode

[typed-sigterm]

Before submitting the PR, please make sure you do the following

• [x] Read the Contributing Guidelines.
• [x] Provide a description in this PR that addresses what the PR is solving. If this PR is going to solve an existing issue, please reference the issue (e.g. close #123).

What is the purpose of this pull request?

• [ ] Bug fix
• [ ] New feature
• [x] Other

Description

improve baidu analytics docs about spa mode

[coveralls]

Pull Request Test Coverage Report for Build 8410438889

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 50.304%

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Totals
Change from base Build 8322558877:	0.0%
Covered Lines:	697
Relevant Lines:	1253

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💛 - Coveralls