[Config] be more specific about bool env var processor

[ghost]

Previous wording was not accurate enough for me because only 0 and 0.0 as integer and float respectively was presented. Alternative change could be:

and all numbers except 0, 0.0, '0' and '0.0'

Let me know if the latter fits better for you.

[javiereguiluz]

I agree that we need to be more precise about this. In fact, while merging, I expanded your contribution a bit to include the examples that you mentioned in the description. See 85ba363

In any case, thanks a lot and congrats on your first Symfony Docs contribution 🎉