title of doc section on factories

[dbu]

the chapter called Message Factory is mentioning the other factories as well.

we should either add another section for those factories, or change the title and make short examples for the uri factory and stream factory on that page.

[dbu]

@sagikazarmark do you have a preference what we should do here?

[sagikazarmark]

Following the logic of PSR-7 the thing is Called Message factories. PSR-17 seems to be better (HTTP Factories).

👍 for adding more examples