fix: namedExport of react-dom/server.js

[MoonBall]

Steps to Reproduce

1. npx create-snowpack-app snowpack-react --template @snowpack/app-template-react --use-yarn
2. cd snowpack-react
3. modify src/App.jsx. see code
4. yarn start

Browser's console will print an error.

Uncaught SyntaxError: The requested module '/web_modules/react-dom/server.js' does not provide an export named 'renderToString'

Changes

The element of autoDetectPackageExports is a file name if it ends with .js rather than index.js.

Before modify: isAutoDetect('react-dom/server.js') returns false.
After modify: isAutoDetect('react-dom/server.js') returns true.

Testing

Test added.

[vercel]

This pull request is being automatically deployed with Vercel (learn more).
To see the status of your deployment, click below or on the icon next to each commit.

🔍 Inspect: https://vercel.com/pikapkg/snowpack/acittkhz5
✅ Preview: https://snowpack-git-fork-moonball-fix-react-dom-serverjs-namedexport.pikapkg.vercel.app

[FredKSchott]

Nice! Good catch