[material-ui][Box] Add basic demo to Box

[zanivan]

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

This PR aims to add a basic demo to the Box component. Even though it's a MUI System component, I believe we could have at least one simple demos for it, since we re-export this component from mui/material.

I also changed the warning callout for an introduction text. I believe this way the link to Box on MUI System docs will stand out more.

[mui-bot]

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• docs/data/material/components/box/box.md

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[danilo-leal]

Little note here just to make sure this is coordinated with @samuelsycamore's PR about restoring and adding content back to the Box page: #40622

[zanivan]

Little note here just to make sure this is coordinated with @samuelsycamore's PR about restoring and adding content back to the Box page: #40622

Oh nice! I thought this tiny tweak could be something good to have merged for now, until we wait for the major revamp of this page. @samuelsycamore let me know what you think, and tell me if you need any help with this :)

[samuelsycamore]

I got caught up in other projects and wasn't able to finish #40622 as quickly as I'd hoped to. 😅 I could pick it back up and probably finish out the content this week—I do think we should just duplicate this doc in its entirety across all of the relevant products, because it's too confusing for many users otherwise. But @zanivan I would love your help revamping the demos if you have ideas! I could tag you in on that revision PR once I'm done with my edits and have you push to that same branch so we can get it done without stepping on each others' toes too much.

[zanivan]

I do think we should just duplicate this doc in its entirety across all of the relevant products

100% agreed!

I could tag you in on that revision PR once I'm done with my edits and have you push to that same branch so we can get it done without stepping on each others' toes too much.

Sure thing! Feel free to ping me when it's ready, I'd love to help with that :)

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Closing this to centralize the work on #40622