Allow to install Symfony 8

[JeanDavidDaviet]

Hello, I know Symfony 8 just have been released, but I tried installing sylius-stack on a new project I'm starting but currently composer prevent to use the package because of version constraints.

I've forked the https://github.com/Sylius/BootstrapAdminUi and https://github.com/Sylius/UiTranslations

but then, there are more dependencies to update.

[loic425]

Hi @JeanDavidDaviet, the Sylius stack will support Symfony 8 on january. A few PRs need to be reviewed on the Resource bundle package.
A PR is already here and it works.

To setup a new project, you can specify the symfony version to use in the Symfony skeleton.