Native Text on iOS doesn't support emoji opacity

[mortoray]

I was able to fix https://github.com/fusetools/fuselibs-public/issues/966 for all targets except native iOS text. Their native renderers just don't support it. For graphics mode I used opacity on the blitting, but for the UITextView I have no simple option. I thought about setting the view opacity, but that would affect more than intended (children and background for example).

Perhaps using an attribute RichText string (NSAttributeText or whatever it is called), might be an option.

[kusma]

I think we would have to add a separate child just for the text, put it in it's own layer, and set the opacity for that.