Docs: Add "React peer dependency is no longer required" section to addon migration guide

[vanessayuenn]

What I did

Added the bit about addon now can remove their react peer dependency.

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

No need!

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>

[jonniebigodes]

@vanessayuenn appreciate you taking the time to put together this pull request and help improve the documentation 🙏 ! I left a small item for you to look into when you have a moment.

Let me know of any questions you may have so we can address them and make this available to our users.

Have a great day.

Stay safe

[JReinhold]

@vanessayuenn @jonniebigodes I added a section referencing the addon kit changes as a migration example.

[jonniebigodes]

@vanessayuenn I left a suggestion for @JReinhold to look into for the migration example. However, the pull request that superseded this one was approved and merged without me having a chance to look into it, and this introduced some documentation issues that could have been easily prevented. Once this is merged, I'll do a proper vetting and polish this to get it into a good state and avoid any follow-up pull requests further down the line.

[vanessayuenn]

@jonniebigodes i will be merging this for now as this PR contains crucial information for addon authors to migrate. Please do the polishing separately though! Appreciate your help here ❤️ .