standard way to mark fingerprinting surface vectors

[marcoscaceres]

@npdoty wrote elsewhere - ignore "ReSpec" and just think "web spec":

Potential feature/enhancement for ReSpec: it would be nice if authors could easily note that a particular section/feature was a potential addition to the fingerprinting surface (or sometimes, a "fingerprinting vector") and then ReSpec would add the nice icon next to it, and alt text regarding browser fingerprinting. This is a convention in HTML, and it would be useful to have it for other specs as well.

Bikeshed issue: speced/bikeshed#964

If we can all use a common SVG file for the icon, that'd be great too. I think @zcorpan has provided one here, which might be freely usable (yes?): whatwg/whatwg.org#64

It's been suggested in updating the guidance for mitigating fingerprinting that we add an explanation for spec authors on an easy way to add the fingerprinting icon to their specs: w3c/fingerprinting-guidance#18
I can provide raw HTML as a suggestion, but if there are even easier Bikeshed/ReSpec ways to do this, all the better.

cc @zcorpan

[marcoscaceres]

@zcorpan wrote in the bug mentioned above:

The fingerprint image in whatwg/whatwg.org#64 when merged will be CC0 per https://resources.whatwg.org/README.md

When the fingerprint PRs are merged, I think the default will be to link to the definition in the Infra standard.

[nigelmegitt]

I found that for dark mode, a simple inversion rule works well for the fingerprinting icon shown at https://www.w3.org/TR/fingerprinting-guidance/#mark-fingerprinting, e.g.:

@media (prefers-color-scheme: dark) {
  img.fingerprint {
    filter: invert(100%);
  }
}

[zcorpan]

@nigelmegitt I think that should be fixed in the SVG itself by using currentColor and color-scheme: light dark. I can submit a PR for the image in resources.whatwg.org.