fix: added return type for build function

[LaurentSanson]

Hi there,

In order to get rid of some deprecation warnings, I'd like to submit this PR.

Warning in question :

User Deprecated: Method "Symfony\Component\HttpKernel\Bundle\Bundle::build()" might add "void" as a native return type declaration in the future. Do the same in child class "Twig\Extra\TwigExtraBundle\TwigExtraBundle" now to avoid errors or add an explicit @return annotation to suppress this message.

Cheers,

Laurent

[github-actions]

Thanks for your pull request! We love contributions.

However, you should instead open a pull request on the main repository:

https://github.com/twigphp/Twig

This repository is what we call a "subtree split": a read-only subset of that main repository.

We're looking forward to your PR there!

[LaurentSanson]

How am I supposed to submit a PR from the main repo as I don't have the rights for it? @fabpot ?

Thanks and have a good one