Fix typo and improve readability and documentation in README.md

[Scr0nch]

The first commit fixes a typo in the first path to the keyboard color control files.

The second commit makes various grammar/structural changes and adds more information about the Omen-specific hotkeys.

[wl2776]

Pressing Fn+Esc indeed generates event 0x21A7 on my notebook.

I've sent acpidump from my notebook to @pelrun and he has found that event code in it. You can see conversation about it in #9.

Then I've accidentally found what key combination generates it by running showkey or evtest (don't remember exactly what it was) and pressing various keys. It is not marked on my keyboard.

[pelrun]

I don't really see much of an readability "improvement" here, it's simply changing my writing style to yours. That said there's at least some added information so I'll try to get over it.