docs: important warning in markdown-features-react.mdx

[dpaulos6]

Pre-flight checklist

• I have read the Contributing Guidelines on pull requests.
• If this is a code change: I have written unit tests and/or added dogfooding pages to fully verify the new behavior.
• If this is a new API or substantial change: the PR has an accompanying issue (closes #0000) and the maintainers have approved on my working plan.

Motivation

When I was registering components to the global scope, as referred in the documentation, @homotechsual helped me out and he told me I might need to restart/rebuild my application after registering the components. Since I didn't find information related to this situation, I added a little warning in case other people encounter the same issue.

Test Plan

I utilized a docusaurus project to preview the changes and used the same warning element that was already in the bottom of the section.

Test links

Deploy preview: https://deploy-preview-10236--docusaurus-2.netlify.app/docs/markdown-features/react/#mdx-component-scope

Related issues/PRs

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⚡️ Lighthouse report for the deploy preview of this PR

URL	Performance	Accessibility	Best Practices	SEO	PWA	Report
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/docs/installation	🟠 67	🟢 96	🟢 100	🟢 100	🟠 88	Report
/docs/category/getting-started	🟠 75	🟢 100	🟢 100	🟢 90	🟠 88	Report
/blog	🟠 70	🟢 100	🟢 100	🟢 90	🟠 88	Report
/blog/preparing-your-site-for-docusaurus-v3	🟠 65	🟢 96	🟢 100	🟢 100	🟠 88	Report
/blog/tags/release	🟠 69	🟢 100	🟢 100	🟢 90	🟠 88	Report
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[slorber]

Thanks for your submission

Unfortunately, I'm unlikely to merge this addition because it looks unnecessarily scary, a bit unclear.

---

The underlying problem is deeper than that: when you create MDXComponents you override the default one we provide, leading to Webpack aliases to change, leading to Webpack config changes.

And afaik to this day there's no clear solution to "hot swap" the Webpack config of the dev server. So anything affecting the Webpack config will require a restart: swizzle, creating MDXComponents (which basically is the same as swizzle), editing some parts of the Docusaurus config...

So, there are still many cases where you'd rather restart the dev server, and we'll try to improve over time, but for now I'm not sure documenting this way in a single place while so many places can be affected would be a good solution unfortunately.

[slorber]

I documented the problem more clearly here, to move this out of my head:

#10238

cc @homotechsual in case you want to understand when this happens better

[dpaulos6]

Understood, thanks for clarifying it for me!