docs: add Webpack and Bun setup guides

[snoopuppy582]

Summary

• Add Webpack setup instructions to the installation and quick-start docs
• Add Bun setup instructions using the Bun plugin's side-effect registration path
• Keep the examples focused on the existing public plugin packages

Tests

• bun x eslint apps/landing/src/app/(detail)/docs/installation/page.mdx apps/landing/src/app/(detail)/docs/quick-start/page.mdx
• bun run --filter landing lint

[codecov]

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