Add direct builder methods

[madsmtm]

Add methods EventLoop::builder and Window::builder, which allows creating the related builders without having to import them. See the examples for how things look cleaner.

Unsure about whether we should deprecate the old methods or not?

• Added an entry to CHANGELOG.md if knowledge of this change could be valuable to users
• Updated documentation to reflect any user-facing changes, including notes of platform-specific behavior
• Created or updated an example program if it would help users understand this functionality
• Updated feature matrix, if new features were added or implemented

[kchibisov]

What's the motivation behind those changes though, besides import? I'm not sure I really get the motivation behind all of that.

[madsmtm]

Only motivation is to reduce the number of imports / things the user has to think about, and to hopefully make it easier to see at a glance which type you're constructing.

[kchibisov]

But it's not like you can't request a builder on your own and it's not like we don't have default, so users will still be able to import/construct it?

[madsmtm]

Definitely true, and there's no other point to deprecating the old methods other than keeping a slightly cleaner API

[daxpedda]

Thanks @madsmtm, the stuff you've done lately improves the API a lot!

[kchibisov]

Needs rebase.