Added @ import to Webpack config, without needing a package

[noviceGuru]

Added @ import

It is the default in NextJS 13 and was not supported by storybook, while I was using it. The way I added it didn't need package to be installed or used

Corrected the type error in config.resolve

Since config.resolve can be undefined, using config.resolve.extensions ran into TypeScript error. by adding a condition to the beginning of the line, I got rid of the TS Error.

Worth to mention

I have a greenfield project in hand, using NextJS13. After adding Storybook for the first components, I ran into an error, that Storybook didn't recognize @ imports that are default in NextJS13.
The solution in the documentation didn't work for me, while the one I added worked just fine.

[jonniebigodes]

@noviceGuru, thanks for taking the time to put together this pull request and help us improve the documentation. Appreciate it 🙏 ! From my end, I left a couple of items that require your attention so that we can merge this.

Additionally, while you're making the changes, do you mind checking the snippets, as they're failing the pretty-docs job to address it requires that you run the yarn pretty-docs script before committing.

Also, thanks for providing some additional context, and with that, I'm going to loop in a fellow maintainer that worked on the Next.js integration and see if this requires an additional pull request for the Next.Js framework documentation to factor in your issue. Sounds good?

@valentinpalkovic can you chime in on this when you have a moment? Appreciate it.

[jonniebigodes]

@noviceGuru one small item for you that you left out. And apologize for not mentioning it earlier. Let me know once you've addressed it and I'll merge it.