Quasar: QEditor needs generic-border-radius applied

[gorango]

Currently, if you apply a border radius to the QEditor, the following will happen:

The corners get cut off by the background color of the toolbar and content.

I have easily updated the CSS but I believe that the editor should have the $generic-border-radius applied to the border and corners of the conflicting elements.

I'm happy to make this PR, just wanna open it up to discussion first.

[nothingismagick]

Go for a PR!

[rstoenescu]

Will be available in beta.19