Docs: Update Storybook to v8

[dylanbox]

Overview

Updates the storybook install to the new version, v8, and updates stories to the new format. This is a prerequisite for implementing the design-system, as we want to use the new storybook inheritance and visual testing suite.

Security

REMINDER: All file contents are public.

• I have ensured no secure credentials or sensitive information remain in code, metadata, comments, etc.
  • Please verify that you double checked that .storybook/preview.js does not contain your participant access key details.
  • There are no temporary testing changes committed such as API base URLs, access tokens, print/log statements, etc.
• These changes do not introduce any security risks, or any such risks have been properly mitigated.

Describe briefly what security risks you considered, why they don't apply, or how they've been mitigated.

Checklist

Testing

• MyDataHelps iOS app
• MyDataHelps Android app
• MyDataHelps website

Documentation

• I have added relevant Storybook updates to this PR as well.
• If this feature requires a developer doc update, tag @CareEvolution/api-docs.

Consider "Squash and merge" as needed to keep the commit history reasonable on main.

Reviewers

Assign to the appropriate reviewer(s). Minimally, a second set of eyes is needed ensure no non-public information is published. Consider also including:

• Subject-matter experts
• Style/editing reviewers
• Others requested by the content owner

[reneefromhold]

Reading this add on will be likely be removed in a future version. Is there a strong reason for including this vs following the recommended instructions? https://www.npmjs.com/package/@storybook/addon-mdx-gfm