feat(client): add onContentUpdated composition API

[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 onContentUpdated 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 13484345740

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 13484327275:	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?

[Mister-Hope]

I think the Vite behavior is expeceted.

Vite use cache header to let browser caches imported modules natively, and when you triggered a HMR, the page is reloaded with the updated module appended with a query t=currentTimeStamp, so it's expected that the root component are also being remounted.

In another word, onContentUpdate hook may never be called, and I think that's why VitePress is only providing a onContentUpdate hook.

The same behavior is observed with Vite Typescript template: https://stackblitz.com/edit/vitejs-vite-q2vxvna7?file=src%2Fcounter.ts&terminal=dev (tested locally as stackblitz perform hotload while editing), where HMR is triggered when modifying counter.ts