Add a fallback for the mdx-components file (#59693)
### What?
Provide a fallback for the `mdx-components` file.
### Why?
Given a user uses the Next.js app directory, and doesn’t have an
`mdx-components` file;
1. If the user has `@mdx-js/react` installed, Next.js shows a cryptic
error message, stating only client components may use React context.
2. If the user doesn’t have `@mdx-js/react` installed, Next.js shows a
cryptic error message, stating `next-mdx-import-source-file` could not
be resolved.
### How?
This fixes 2 by providing a fallback.
I suggest fixing 1, by completely removing all references to
`@mdx-js/react` from the project.
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Co-authored-by: JJ Kasper <jj@jjsweb.site>
