perf: move the <pre> extra attribute to preWrapper

[pengzhanbo]

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

• Read the Contributing Guidelines.
• 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
• Other

Description

- <div class="language-*">
-   <pre class="shiki nord vp-code" style="background-color:#2e3440ff;color:#d8dee9ff" tabindex="0">

+ <div class="language-*" style="background-color:#2e3440ff;color:#d8dee9ff" tabindex="0">
+   <pre class="shiki nord vp-code">

[coveralls]

Pull Request Test Coverage Report for Build 9268209463

Details

• 6 of 6 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.08%) to 56.469%

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Totals
Change from base Build 9265804820:	0.08%
Covered Lines:	994
Relevant Lines:	1574

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💛 - Coveralls

[Mister-Hope]

哦我想起来了，我认为这东西默认值最好就是false。另外如果只设置theme而非themes，这个选项是不是没有作用？