fix: mark prism-extend as side-effectful to fix CJS language registration

[mdeliatf]

Description

Additional Prism languages registered in prism-extend.ts worked locally and in Storybook but were silently dropped when hub-ui was built via Docker CI.

Root cause

package.json had "sideEffects": false, which tells bundlers they can safely tree-shake any module that only re-exports values from externals. Rolldown exploited this when generating the CJS build: since prism-extend.ts re-exports Prism from prism-react-renderer (an external dependency), it inlined the import directly and never generated prism-extend.cjs, losing all the language registration side effects in the process.

The ESM build was unaffected because ESM preserves module identity more strictly. Local development was also unaffected because webpack skips tree-shaking in dev mode.

The combination that triggered the bug: CJS resolution (Next.js production build) + tree-shaking enabled (webpack production mode) + sideEffects: false (told rolldown the module was pure).

How to test

1. Pull the updated Faency package into hub-ui
2. Run next build (or trigger a Docker CI build) this exercises the CJS path with tree-shaking enabled
3. Open a page that renders a CodeBlock with one of the previously broken languages (e.g. hcl, toml, docker, bash) and verify syntax highlighting is applied correctly
4. Confirm the same page works in the deployed Docker image

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🎉 This PR is included in version 12.3.3 🎉

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