When it comes to building themes in WordPress, one of the nicest things that you can do for your users is to implement a stylesheet specifically for the editor so that they get a true WYSIWYG experience.
To be more specific, that is you can (and should!) add a stylesheet specifically for the WYSIWYG editor in the WordPress Dashboard. This stylesheet is normally called `editor-style.css`, but can actually be called whatever it is that you’d like permitting that you enqueue it properly.
With the popularity of web fonts rising – such as those from Google – you have to take a slightly different approach when implementing them in the context of the editor rather than the typical way of doing so with server side hooks.