Be able to copy colored, formatted code

It would be nice when in `tree` mode to be able to copy the JSON, and when in `code` mode copy the colorified, formatted code. So you can paste it in for example Google Docs or MS Word.

Ref: https://github.com/josdejong/jsoneditor/issues/891#issuecomment-593619977

> I only have one suggestion for the app, I would like to have the option to colorfy the JSON when pasting it in Google Docs files, I've been using the following app to do such thing http://www.bodurov.com/JsonFormatter/, so I copy and paste the JSON from your app to the other and then I paste the JSON with the colors in my documents. Is it possible to do the same with yours?

See also: #252, #127