[docs] Update callouts design

[danilo-leal]

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

In light of Sam's recent callout content standardization (#35361), thought about doing some light updates on their design. It's worth highlighting the info variant, that now it's way more subtle & grayish, which is to be different from the code block. @siriwatknp one interesting upgrade we should think about doing is displaying icons by default⎯just a container with text seems not enough to stand out on the documentation block of text, and the icons might help exactly with that!

Preview link:
https://deploy-preview-35390--material-ui.netlify.app/experiments/docs/callouts/

[gerdadesign]

Looking good! Is there any way to force the emoji version to show up instead of the text version?

Text	Emoji

[siriwatknp]

@danilo-leal Sounds good. How about adding -icon at the end to show the default icon?

:::info-icon
Some content
:::

cc @samuelsycamore

[siriwatknp]

Also, you might want to remove the .gitignore change 😅.

[mapache-salvaje]

@danilo-leal Sounds good. How about adding -icon at the end to show the default icon?
cc @samuelsycamore

That's a great idea! I was thinking it would be nice to have the option not to include an icon in certain situations.

[danilo-leal]

Sweet, totally agree with both having the icons and the optionally of not having them for specific use-cases 👍
@siriwatknp .gitignore removed!

[mui-bot]

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[siriwatknp]

@danilo-leal Sounds good. How about adding -icon at the end to show the default icon?
cc @samuelsycamore

That's a great idea! I was thinking it would be nice to have the option not to include an icon in certain situations.

@samuelsycamore Me too, but then we need to change all of the current callouts to not include the icon which will be a huge PR.

[danilo-leal]

@siriwatknp Let me know when this PR is ready to go! The icons should probably be implemented in a separate one 😬

[siriwatknp]

👍 LGTM. I pushed an update for the alpha color.