docs(button): custom storybook docs from spectrum-two

[jawinn]

Description

Moves over custom Button documentation from the spectrum-two branch, and integrates it with the current organization of stories in main. As part of the effort to migrate the docs site to Storybook. Includes a custom .mdx file, additional docs-only stories, and some supporting templates.

How and where has this been tested?

Please tag yourself on the tests you've marked complete to confirm the tests have been run by someone other than the author.

Validation steps

• Storybook Button docs from the spectrum-two branch have been migrated and are displaying correctly: PR link

Regression testing

Validate:

1. The documentation pages for at least two other components are still loading, including:

• The pages render correctly, are accessible, and are responsive.

2. If components have been modified, VRTs have been run on this branch:

• VRTs have been run and looked at.
• Any VRT changes have been accepted (by reviewer and/or PR author), or there are no changes.

To-do list

• I have read the contribution guidelines.
• I have updated relevant storybook stories and templates.
• If my change impacts other components, I have tested to make sure they don't break.
• If my change impacts documentation, I have updated the documentation accordingly.
• ✨ This pull request is ready to merge. ✨

[changeset-bot]

⚠️ No Changeset found

Latest commit: 4f71a63

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[github-actions]

🚀 Deployed on https://pr-3069--spectrum-css.netlify.app

[github-actions]

File metrics

Summary

Total size: 4.10 MB^*

🎉 No changes detected in any packages

* Size determined by adding together the size of the main file for all packages in the library.
* Results are not gzipped or minified.
* An ASCII character in UTF-8 is 8 bits or 1 byte.

[rise-erpelding]

I did not review these parts of the documentation you added in #2600, so this is my first time really looking over it! The custom .mdx template seems really necessary here to keep everything organized, and I really like what you've done with the templates to display the different groupings and variants of buttons, they feel really efficient and easy to reason through.

I left a couple of questions/opinionated suggestions that don't necessarily require changes and wouldn't necessarily hinder approval/merge. Otherwise, this looks great!