Docs: Add Next.js framework doc

[kylegach]

What I did

Documents Storybook for Next.js framework

Based on

• https://github.com/storybookjs/storybook/tree/next/code/frameworks/nextjs
• https://storybook.js.org/blog/integrate-nextjs-and-storybook-automatically/

Checklist for Contributors

Testing

The changes in this PR are covered in the following automated tests:

• stories
• unit tests
• integration tests
• end-to-end tests

Manual testing

1. Follow the steps in the contributing instructions for this branch, framework-doc-nextjs

Documentation

• Add or update documentation reflecting your changes
• If you are deprecating/removing a feature, make sure to update
  MIGRATION.MD

Checklist for Maintainers

• When this PR is ready for testing, make sure to add ci:normal, ci:merged or ci:daily GH label to it to run a specific set of sandboxes. The particular set of sandboxes can be found in code/lib/cli/src/sandbox-templates.ts

• Make sure this PR contains one of the labels below:

  Available labels

  • bug: Internal changes that fixes incorrect behavior.
  • maintenance: User-facing maintenance tasks.
  • dependencies: Upgrading (sometimes downgrading) dependencies.
  • build: Internal-facing build tooling & test updates. Will not show up in release changelog.
  • cleanup: Minor cleanup style change. Will not show up in release changelog.
  • documentation: Documentation only changes. Will not show up in release changelog.
  • feature request: Introducing a new feature.
  • BREAKING CHANGE: Changes that break compatibility in some way with current major version.
  • other: Changes that don't fit in the above categories.

🦋 Canary release

This PR does not have a canary release associated. You can request a canary release of this pull request by mentioning the @storybookjs/core team here.

core team members can create a canary release here or locally with gh workflow run --repo storybookjs/storybook canary-release-pr.yml --field pr=<PR_NUMBER>

[chantastic]

Love seeing this. That's a lot to cover, nicely done.

[jonniebigodes]

I took a preliminary pass at this and there's some work that needs to done for now so that we can get this into a good shape before we can take another pass at it and polish it up in terms of structure.

[jonniebigodes]

Can you add a comment mentioning the file name so that when rendered in the documentation, the snippet component can be interpreted without a blank title? Also, while we're at it convert this to a snippet file and introduce a JSX and a TSX variant, and also ensure this is capitalized properly.

[kylegach]

This is demonstrating usage of a Next.js feature, not a Storybook one. This is not something folks will be copy/pasting, and if they do, it'll be the <Image> portion, which will be identical for JS & TS. I don't think the overhead of multiple snippets is worth the small benefit.

[kylegach]

@jonniebigodes — Ready for your re-review!