chore: add missing Vue support for Vercel builds

[trusktr]

Summary

We currently have two index.html files (why is that again?). One file was not loading Vue stuff.

Without the Vue support in Vercel builds, we were unable to fully verify pull request builds, therefore unable to confirm if Vue broke or not. Now we can manually check Vue functionality for PRs.

What kind of change does this PR introduce?

Add Vue support to the index.html file that didn't have it.

For any code change,

• Related documentation has been updated if needed
• Related tests have been updated or tests have been added

Does this PR introduce a breaking change? (check one)

No

If yes, please describe the impact and migration path for existing applications:

Related issue, if any:

Tested in the following browsers:

• Chrome
• Firefox
• Safari
• Edge

[vercel]

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Name	Status	Preview	Comments	Updated (UTC)
docsify-preview	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Jul 18, 2023 10:03am

[Koooooo-7]

Hi @trusktr , That's what I work on the 2 index.html sometimes.

One is /doc/index.html, which we could host it as docsify live site, which import external .../docsify@4/lib/docsify.min.js (we could check current live behavior).
One is /index.html, thats for the dev locally, which import /lib/docsify.js (we could check the dev/changed behavior).

We could have a compare on them easily.

Maybe we should sync common files index.html, README...on time in case of having some different except dev changes.