Issue title: No autofocus on mobile
 Issue body: Hello !

When the editor is initialized, I would like to autofocus it (event on mobile). It works on my desktop, but nothing happened on mobile. I would like the keypad to open automatically.

##### Steps to reproduce the problem.
https://jsfiddle.net/bysp4rxv/7/

##### OS.
iOS 10

##### Browser.
Safari

 Comments: 
 Comment 0: On iOS it is possible to focus inside an input only after the user makes an action (e.g. clicking a button). This is a limitation set by Apple and there is no work around for it.
 Comment 1: Ok, but I have the same thing on Android...
{'source': 'GithubIssues', 'repo_name_with_owner': 'froala/wysiwyg-editor', 'issue_id': 237770884, 'repo_stars': 5275.0}