Make it easier for users to learn on how to style widgets

[Wiktor Walc]

I just spend a good 5 minutes (knowing where to search more or less) to find how am I supposed to define styles for widgets.

Suggestion:

• To the default styles.js add at least two sample widget styles, for embed media and image 2.
• To the default styles.js on top of it add a link to ​http://docs.ckeditor.com/#!/guide/dev_styles-section-style-rules

[Tade0]

Added some new styles. Changes pushed to ​branch:t/16644.

[kkrzton]

Overall it looks good.

I noticed one issue - when you have widget focused and apply/remove widget style the combo value (in closed state) does not update. It updates only after refocusing widget. However, this is not caused by the changes made for this task, but rather by the way stylescombo detects style changes and updates itself. Separate issue for this should be created.

I will ask @wwalc to validate the styles (from the user perspective as he requested it). If it is ok, I will merge it to the major.

[kkrzton]

Pushed changes to ​t/16644.

[Tomasz Jakut]

LGTM.

[kkrzton]

Merged to major with ​fbe67fa.