Add new themes to Storybook + generate VRT snapshots

[langermank]

Adding new themes to the Storybook theme picker, and generating snapshots 😄

Review link: https://github.com/primer/react/pull/6338/files?file-filters%5B%5D=.css&file-filters%5B%5D=.json&file-filters%5B%5D=.jsx&file-filters%5B%5D=.ts&show-viewed-files=true

[changeset-bot]

⚠️ No Changeset found

Latest commit: 2ddea62

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

[github-actions]

👋 Hi, this pull request contains changes to the source code that github/github depends on. If you are GitHub staff, we recommend testing these changes with github/github using the integration workflow. Thanks!

[github-actions]

size-limit report 📦

Path	Size
packages/react/dist/browser.esm.js	92.26 KB (0%)
packages/react/dist/browser.umd.js	92.35 KB (0%)

[Copilot]

Copilot wasn't able to review any files in this pull request.