Ckeditor5: Remove command icon

[mlewand]

We need a nice icon for the feature. In the initial rollout I used erase icon that could be reused (actually font/bg color will reuse it too).

What do you think about the icon? Do we want to add a new one or is it ok to reuse the existing one?

[oleq]

This needs a research. We need to come up with an icon the users are familiar with, preferably the most common among the word processors.

[dkonopka]

I've made a quick research, which says that almost everyone is using T with × sign (or strikethrough in GDocs case).

FYI: The last one example - A with rubber is a Word usage.

I'll propose something for CK5 soon.

[oleq]

Part of now https://github.com/ckeditor/ckeditor5-remove-format/pull/1.