feat(cli): support mjs&cjs as default config file

[hardfist]

Summary

since we support mjs as config file now, we should support rspack.config.mjs as default config file

Related issue (if exists)

Types of changes

• Docs change / Dependency upgrade
• Bug fix
• New feature / Improvement
• Refactoring
• Breaking change

Checklist

• I have added changeset via pnpm run changeset.
• I have added tests to cover my changes.

[changeset-bot]

🦋 Changeset detected

Latest commit: 1d4aeaf

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 18 packages

Name	Type
@rspack/cli	Patch
benchmarkcase-rspack-react-refresh	Patch
@rspack/playground	Patch
@rspack/postcss-loader	Patch
@rspack/dev-client	Patch
@rspack/dev-middleware	Patch
@rspack/dev-server	Patch
@rspack/plugin-html	Patch
@rspack/plugin-minify	Patch
@rspack/plugin-node-polyfill	Patch
@rspack/core	Patch
@rspack/binding-darwin-arm64	Patch
@rspack/binding-darwin-x64	Patch
@rspack/binding-linux-x64-gnu	Patch
@rspack/binding-win32-x64-msvc	Patch
@rspack/binding	Patch
@rspack/fs	Patch
webpack-test	Patch

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