Gradient not working on strokes

[kcap]

Describe the bug
Strokes with gradient fill not working

To Reproduce
See example

https://raw.githack.com/yWorks/svg2pdf.js/master/index.html?svg=%253Csvg%2520version%253D%25221.1%2522%2520id%253D%2522Layer_1%2522%2520xmlns%253D%2522http%253A%252F%252Fwww.w3.org%252F2000%252Fsvg%2522%2520xmlns%253Axlink%253D%2522http%253A%252F%252Fwww.w3.org%252F1999%252Fxlink%2522%2520x%253D%25220px%2522%2520y%253D%25220px%2522%2520viewBox%253D%25220%25200%2520595.28%2520841.89%2522%2520style%253D%2522enable-background%253Anew%25200%25200%2520595.28%2520841.89%253B%2522%2520xml%253Aspace%253D%2522preserve%2522%253E%250A%2520%2520%253Cdefs%253E%250A%2520%2520%2520%2520%253ClinearGradient%2520id%253D%2522SVGID_1_%2522%2520gradientUnits%253D%2522userSpaceOnUse%2522%2520x1%253D%2522166.3525%2522%2520y1%253D%2522320.284%2522%2520x2%253D%2522414.959%2522%2520y2%253D%2522320.284%2522%253E%250A%2509%253Cstop%2520offset%253D%25220%2522%2520style%253D%2522stop-color%253A%2523FFF33B%2522%253E%253C%252Fstop%253E%250A%2509%253Cstop%2520offset%253D%25221%2522%2520style%253D%2522stop-color%253A%2523E93E3A%2522%253E%253C%252Fstop%253E%250A%253C%252FlinearGradient%253E%250A%2520%2520%253C%252Fdefs%253E%250A%253Cstyle%2520type%253D%2522text%252Fcss%2522%253E%250A%2509.st0%257Bfill%253A%252339B54A%253Bstroke%253Aurl%28%2523SVGID_1_%29%253Bstroke-width%253A15%253Bstroke-miterlimit%253A10%253B%257D%250A%253C%252Fstyle%253E%250A%250A%253Crect%2520x%253D%2522173.85%2522%2520y%253D%2522219.62%2522%2520class%253D%2522st0%2522%2520width%253D%2522233.61%2522%2520height%253D%2522201.32%2522%253E%253C%252Frect%253E%250A%253C%252Fsvg%253E%250A

[HackbrettXXX]

Yes, gradients on strokes are not supported at the moment. We're happy to merge a PR. However, jsPDF also does not support this ATM.

I've updated #82.