React: Add addon-onboarding as part of init

[yannbf]

closes #22872, closes #22870

What I did

This PR adds @storybook/addon-onboarding as part of the initiate step and execute dev with --initial-path=/onboarding to the CLI of (for now) React projects

This should not be merged until the addon-onboarding is ready.

How to test

1. Build all packages
2. Create a new project with the CLI e.g. ./code/lib/cli/bin/index.js init
3. Expect Storybook to open with the onboarding flow

Checklist

• Make sure your changes are tested (stories and/or unit, integration, or end-to-end tests)
• Make sure to add/update documentation regarding your changes
• If you are deprecating/removing a feature, make sure to update
  MIGRATION.MD

Maintainers

• If this PR should be tested against many or all sandboxes,
  make sure to add the ci:merged or ci:daily GH label to it.
• Make sure this PR contains one of the labels below.

["cleanup", "BREAKING CHANGE", "feature request", "bug", "documentation", "maintenance", "dependencies", "other"]