Fix storybook mdx plugin

[rajsite]

Pull Request

🤨 Rationale

Improves #825. Found that the current "@mdx-js/react": "*" version was resolving in package-lock.json to the latest "@mdx-js/react" at v2 which is an actual breaking change for storybook.

👩‍💻 Implementation

Instead matched the version specifier with the one in the storybook package version and verified that the package-lock only shows one version.

🧪 Testing

Built locally

✅ Checklist

• I have updated the project documentation to reflect my changes or determined no changes are needed.

[jattasNI]

This is definitely an improvement. Though the Getting Started page still seems to have styling issues (e.g. uses browser default font and image is too big).

I changed the PR description not to resolve #825 but I'm going to complete the PR since it's a step forward. I'll update the issue to describe what needs validating when we update to the next Storybook major version.