Copying linked files fails with embedded SVG <a> elements

[rakuco]

#132 seems to have introduced a bug that can be reproduced when running build.js on https://github.com/w3c/sensors/2b77580c9d7fb2ecb68c5ef264d2ce5c69f5c901/main/index.bs.

The output is not very helpful and looks like this:

    [INFO] Finding relevant assets…
      [INFO] From /index.bs.built.html…
      Invalid URL

Running things manually and adding some debugging, the problem is in sidvishnoi/subresources@f7061df: getLinks() uses "a[href]" as a selector, which ends up including <a> elements inside <svg> documents. These <a> elements are SVGAElements though, and their href attribute returns an object instead of a string, and it breaks findAssetsToCopy in this repository.

I'm filing this issue because I'm not sure if the idea was to ignore links in embedded SVG or if they need to be properly parsed instead (the links in the Generic Sensor spec refer to anchors in the actual spec and thus outside the SVG document, for example).

[rakuco]

cc @sidvishnoi

[sidvishnoi]

Thank you for finding the cause. I'll find some time in day tomorrow to fix it and improve the logging.