fill color by url does not work

[joda-divid]

After the change to use lowerCase for fill/stroke/color even in-svg definitions went to lowerCase and do no longer match, e.g. fill="url(#Pattern)"

Suggesting exception to lowerCase if the string contains url.

(This will likely cause problems if anyone uses the namedColor burlywood and spells it with upperCase, but since this is not intended to be a long term solution but only while alafr/SVG-to-PDFKit#152 isn't fixed, that drawback feels acceptable to me.)