Summary

In context of packages declared as type module in package.json, using config.js does not work due to expecting ES modules syntax in that file and vuepress still trying to userequire() for loading. In such a context, Node.js supports extension.cjs to individually mark a file as CommonJS style. However, VuePress didn't recognize those files due to lack of explicitly looking for them. And that's what this PR is for.

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style update
• Refactor
• Docs
• Build-related changes
• Other, please describe:

If changing the UI of default theme, please provide thebefore/after screenshot:

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

• Yes
• No

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

The PR fulfills these requirements:

• When resolving a specific issue, it's referenced in the PR's title (e.g.fix #xxx[,#xxx], where "xxx" is the issue number)

You have tested in the following browsers: (Providing a detailed version will be better.)

• Chrome
• Firefox
• Safari
• Edge
• IE

If adding anew feature, the PR's description includes:

• A convincing reason for adding this feature
• Related documents have been updated
• Related tests have been updated

To avoid wasting your time, it's best to open afeature request issue first and wait for approval before working on it.

Other information: