fix: ERR_REQUIRE_ESM error when project type is set to module

[titouanmathis]

There is currently a bug when building Vitepress in a project with its type set to module in the package.json file. The temporary directory for the SSR build is bundled in CJS format with .js extension. In a project whose type is set to module, these files are considered ESM and cannot be required(), see this reproduction repository to test the bug.

I was able to fix the issue by adding a package.json file in the temporary directory with type set to commonjs.

[brc-dd]

No it won't fix #476, although this PR might still be valid. That issue was about using ESM only packages like d3@7 with VitePress. Your PR doesn't fix that, it only fixes if someone is using CommonJS packages with VitePress but has type: module set in their package.json. Your change will throw a different error but it still won't work. Check brc-dd/vitepress-type-module-reproduction.

[titouanmathis]

@brc-dd you are right, this does not fix #476, my bad. I updated the description to remove the mention of the issue.

[brc-dd]

closing this in favor of #856