fix(vscode): fix build and publish, reduce extension size

[kermanx]

• fix publishing of vscode extension
• fix build config
• dedupe prettier
• prevent multiple unused files from being packed into .vsix

Blocked by oxc-project/oxc#11840. In fact this problem is introduced by the migration to tsdown, but not observed because the publishing of vscode extension has been broken.

[netlify]

✅ Deploy Preview for slidev ready!

Name	Link
🔨 Latest commit	1001d2a
🔍 Latest deploy log	https://app.netlify.com/projects/slidev/deploys/686e21fe1b1a4a0008a13ded
😎 Deploy Preview	https://deploy-preview-2207--slidev.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify project configuration.

[pkg-pr-new]

Open in StackBlitz

@slidev/client

npm i https://pkg.pr.new/slidevjs/slidev/@slidev/client@2207

create-slidev

npm i https://pkg.pr.new/slidevjs/slidev/create-slidev@2207

create-slidev-theme

npm i https://pkg.pr.new/slidevjs/slidev/create-slidev-theme@2207

@slidev/parser

npm i https://pkg.pr.new/slidevjs/slidev/@slidev/parser@2207

@slidev/cli

npm i https://pkg.pr.new/slidevjs/slidev/@slidev/cli@2207

@slidev/types

npm i https://pkg.pr.new/slidevjs/slidev/@slidev/types@2207

commit: 1001d2a