[core] Redirect to X in dev mode

[oliviertassinari]

It makes it easier to work across the product. I can click on MUI X and it will direct me to the right localhost URL.

[mui-bot]

No bundle size changes

Generated by :no_entry_sign: dangerJS against 05537143a96ee7f5da1779d3c9c0561db77db172

[oliviertassinari]

During the weekend, I was switching back end forth to make changes across the two repositories. Sometimes, I was landing on a 404 page, and was like: "arrrf".

One possible problem with the implementation is that if https://github.com/mui/material-ui adds more marketing pages here, then it will break. The redirection logic would have to start to be quite complex.

[oliviertassinari]

I'm giving up on the idea, I suspect that we will need to have a dedicated marketing page for the data grid in the future. Thanks for the feedback!