Add upcoming 4.x release to docs

[acoulton]

No description provided.

[stof]

I'm wondering whether we should keep a master branch being 3.x and having a 4.x branch for 4.x. Shouldn't we rather use 3.x for the maintenance branch and keep the default branch for the latest dev version ?

[acoulton]

I was actually about to propose that we rename the master branch to 3.x so that the branches are all explicit. IMO this would be clearer for us and for contributors while we're supporting multiple versions. That follows how e.g. symfony and doctrine do their branching.

It would also be easier then to configure branch protection rules for release branches, github actions build triggers etc as anything *.x is a release branch.

I think we can configure the branch alias the other way round in our composer.json so that the available versions on packagist aren't affected.

The only downside would be that any external links to specific files in the master branch e.g. https://github.com/Behat/Behat/blob/master/CHANGELOG.md would be broken, although equally linking to a file in a branch like that is never guaranteed to be long-term stable.

[carlos-granados]

Didn't know about the Symfony 8 stuff, it's great that we mention it