[docs] Add demo for styling charts with sx props

[derek-0000]

Issue: #12633

Result:

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

[mui-bot]

Deploy preview: https://deploy-preview-12791--material-ui-x.netlify.app/

Updated pages:

• docs/data/charts/styling/styling.md

Generated by 🚫 dangerJS against 81fb99e

[alexfauquette]

Thanks for this nice example. For info, you can only write the tsx file and run the yarn docs:typescript:formatted command to generate the js one.

I modified a bit the sx to use the theme such that the demo adapt on the light/dark theme.

sx={(theme) => ({ ....  })}

If it's ok for you, wen merge 👍

[derek-0000]

Thanks for the feedback. The end result looks great!