Support Transparency / Transparent backgrounds

[vade]

Not sure if its intended, but a custom Theme that specifies an alpha that isnt 1, is rendered moot by the enclosing scroll view (at least on macOS) being drawn.

A quick fix i found was was updating the tile() function on CodeView

line 1072

#elseif os(macOS)
    enclosingScrollView?.drawsBackground = false

This couldn't go in init, as the enclosingScrollView isnt created yet.

Thanks for an awesome project!

[mchakravarty]

Thank you for the suggestion. To be honest, it didn't occur to me that one might set a background colour that is partially transparent.

I think, this can go into the section at the top of tile(), where the floating subviews are set.