[docs] Mention Toolpad in Example projects section

[prakhargupta1]

'Example projects' made more sense over Discover more -> 'Related projects' as the placement for Toolpad.
Also linked example folder from Toolpad repo.

Preview: https://deploy-preview-44391--material-ui.netlify.app/material-ui/getting-started/example-projects/

[mui-bot]

Netlify deploy preview

• docs/data/material/getting-started/example-projects/example-projects.md

Bundle size report

No bundle size changes (Toolpad)
No bundle size changes

Generated by 🚫 dangerJS against 772d026

[samuelsycamore]

If we add Toolpad here, then this sentence at the top of the doc is no longer technically true:

The following integration examples are available in the /examples folder of the Material UI GitHub repository. [...]

So if we want to proceed, I think we need to rewrite this whole section:

The following integration examples feature Material UI paired with other popular React libraries and frameworks, so you can skip the initial setup steps and jump straight into building.

[oliviertassinari]

On what's the right place for add Toolpad in the docs, it feels like it's the same case as #44315 (comment).

[prakhargupta1]

So if we want to proceed, I think we need to rewrite this whole section:

Just did this change, but as per Olivier's PR we may want to put it under Related projects > App starters. I'll let you decide the placement that makes most sense.