Add next.js information in static-site-generators

[aromeoes]

Describe your changes

Next.js guide was missing, even though it was specified in the top of the site

What issue(s) does this address?

Lack of next.js upload example

Does this update depend on any other PRs?

no

Checklist before requesting a review

• Passing the beta version of the Check Markdown links for modified files check. Action results can be viewed here.

Checklist before merging

• Passing all required checks (The beta Check Markdown links for modified files check is not required)

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Suggested change

	Refer to Next.js's [output](https://nextjs.org/docs/app/api-reference/next-config-js/output) guide to install Ruby and Jekyll.
	Refer to Next.js's [output](https://nextjs.org/docs/app/api-reference/next-config-js/output) guide to configure next.js to configure static output.

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Please use npx next and the correct command and add information about the output folder.

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See coments

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Sites generated with next.js also need to set trailingSlash to true in next.config.js to ensure that a folder is created with an index.html instead of path.html in the root folder.

When used with output: "export" configuration, the /about page will output /about/index.html (instead of the default /about.html). https://nextjs.org/docs/app/api-reference/config/next-config-js/trailingSlash

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Closing as this has been replaced by #1999