[docs-infra] Add code block header classes

[danilo-leal]

• I have followed (at least) the PR section of the contributing guide.

An attempt at adding headers to code blocks that are usually useful when we want to display the file name of a certain code snippet. I have a feeling this is not the most efficient/elegant way to do 😅 I still wanted to take a shot at pulling this off, but there might be better ways where the DX is similar to the custom <codeblocks> component, and cleaner. Possibly something like:

<codeblock header="File name">

{...code here}

</codeblock>

Closes #38381 (or not — in any case, let me know! I'm happy to ditch this PR if we don't think it's useful.)
Preview: https://deploy-preview-41487--material-ui.netlify.app/experiments/docs/codeblock/

In the ideal world, we'd have a solution that would appear like a breadcrumb, displaying the full path from where a code snippet belongs. This is not covered in this PR and another reason why this is potentially not the best solution 😬

[mui-bot]

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[siriwatknp]

@danilo-leal Here is my proposal to follow Docusaurus.

[siriwatknp]

👍 Thanks for starting this! I almost forgot about it, sorry for the delay.

[siriwatknp]

@danilo-leal feel free to bypass CI and merge if you want.