SVG: Missing support for CSS "currentColor" stroke tag

Example SVG: https://github.com/tabler/tabler-icons/blob/master/icons/copy.svg

A possible fix this is to just stick this in parseColour (juce_SVGParser.cpp):

        if (text == "currentColor")
            return Colours::black;

The only issue is not having the flexibility to configure the currentColor… Not sure if that matters really.

More information on the tag: https://css-tricks.com/cascading-svg-fill-color/