docs: reorder README sections in order of importance

[empicano]

Hi Frederik!

Again with the README 😄 I tweaked a few little things, and reordered the sections, among others to move the Note for Windows users higher, as there are quite a few people who seem to overlook this. (Btw. is there anything that speaks against implementing the switch to the SelectorEventLoop directly in the code? I guess changing the loop silently is not a very nice pattern.)

~ Felix

[JonathanPlasse]

Why delete the requirement section?

[empicano]

I didn't delete it, I just merged it with the installation section 😉

[frederikaalund]

Good idea to move the "Note for Windows users" section up. 👍 We get a frequent stream of new issues due to that.

(Btw. is there anything that speaks against implementing the switch to the SelectorEventLoop directly in the code? I guess changing the loop silently is not a very nice pattern.)

Technically, there is no barrier. :) It's just intrusive to switch the loop like that IMHO. What we could do, is to issue a warning if the user attempts to use the library with a non-supported event loop. In that warning, we can instruct the user to switch the event loop. I weldcome a PR with that change. 👍

Back to this PR itself. LGTM. Thanks!

~Frederik