[styles] Add React 18 to peer dep

[brijeshb42]

Fixes #40477

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

[mui-bot]

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[michaldudak]

@mui/styles is not compatible with React 18.

[jinsley8]

@mui/styles is not compatible with React 18.

The docs have some conflicting information about styles. Is @mui/material/styles preferred over @mui/styles now in v5?

https://mui.com/material-ui/migration/migration-v4/#material-ui-v5-and-mui-styles
https://mui.com/material-ui/migration/v5-style-changes/#%E2%9C%85-update-createstyles-import

[samuelsycamore]

@mui/styles is not compatible with React 18.

The docs have some conflicting information about styles. Is @mui/material/styles preferred over @mui/styles now in v5?

https://mui.com/material-ui/migration/migration-v4/#material-ui-v5-and-mui-styles https://mui.com/material-ui/migration/v5-style-changes/#%E2%9C%85-update-createstyles-import

I can see why these sections could cause confusion out of context, but the migration docs are explaining how to progressively migrate to v5 without migrating away from @mui/styles immediately, which is something that you should do eventually, as the doc states:

Note that you may continue to use JSS for adding overrides to the components (e.g. makeStyles, withStyles) even after migrating to v5. Once you've completed the rest of the v5 upgrade, we recommend progressively moving over to the new styling engine.

This process is covered in Migrating from JSS.

So it's showing you how to continue to use the (deprecated) @mui/styles package with v5 while you're still in the process of migrating. Does that make sense?

@mui/styles was deprecated with the release of v5 in 2021, so it does not and will not support React 18+. You should always use @mui/material/styles instead, which is the package of Emotion-based tools that replaced the earlier JSS versions.

[jinsley8]

@samuelsycamore Thanks for clarifying.

Turns out I had @mui/styles installed but I'm not using it in any files. Everything was already updated to @/mui/material/styles. I've since deleted @mui/styles.