feat(client): add markdown content hooks

[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
• Documentation update
• Other

Description

When the markdown content changes, using the built-in Vue lifecycle hooks does not work well, so the onContentMounted / onContentChange / onContentBeforeUnmount hook has been added to properly listen for changes in the content.

This applies to scenarios such as medium-zoom or photo-swipe that require reinitialization when the page content changes.

[coveralls]

Pull Request Test Coverage Report for Build 12308970701

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 71.722%

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Totals
Change from base Build 12271244431:	0.0%
Covered Lines:	648
Relevant Lines:	906

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💛 - Coveralls

[Mister-Hope]

uepress/docs also needs a PR

[pengzhanbo]

uepress/docs also needs a PR

vuepress/docs#44

[meteorlxy]

e2e tests are required

[pengzhanbo]

@meteorlxy @Mister-Hope
I have rewritten this PR and added relevant e2e tests referencing hmr, but it is not working properly in vite. Can you help me resolve this?