fix(media-area): add svg icon support to media area items

[germanocaumo]

What does this PR do?

Support svg icon in media area items like it is for action bar buttons (see #167)

[GuiLeme]

All looks fine, I am just concerned about this being a breaking change. Since 3.1 has not been released yet, I'd say it's fine, but I'd feel more comfortable with a confirmation from your side that it would not be a problem. @Arthurk12, can you comment on this?

[Arthurk12]

Thanks for pointing it out, @GuiLeme. We are aware that this modification is going to break the MediaAreaItems API.

For the future we could enhance and make the API consistent for all extensible areas by:

1. Changing the icon argument from object to string | object;
2. Allow SVG icons for all extensible areas as you pointed out here;

[GuiLeme]

@Arthurk12 sounds good, so let's maintain this PR as is and for the following one (adding SVG for all icons) we can do the strategy you brought up. That will be done likely in 0.0.x, but with the sync merge this will be resolved for 0.1.x as well.