Added ACE editor support

[Zhigalin]

No description provided.

[tonsky]

Well, ACE isn’t a standalone editor, is it? So it should be covered by “Browsers support” section already?

[Zhigalin]

Well, a in-browser code editor is a bit more complex than a simple textarea...
Actually I don't know how it could work because every character is placed inside a separate div... But it works.

[MadcapJake]

Isn't Atom based on Ace? If so, it actually groups characters by span via a grammar tokenizer. So if the language grammar groups two chars together, it will come up ligaturized in Fira Code. A cursory inspection of github seems to support this (though each row is actually a <tr>).

[tonsky]

Ok, I added ACE and CodeMirror to the browsers section