No support for multiple URLs in srcset

[alexpls]

Part of the HTML 5.1 spec defines the srcset attribute on img elements where multiple URLs can be specified on one img to use in different situations (high pixel density displays, small monitors, etc).

An example of this taken from the draft w3c spec looks like:

<img src="/uploads/100-marie-lloyd.jpg"
      srcset="/uploads/150-marie-lloyd.jpg 1.5x, /uploads/200-marie-lloyd.jpg 2x"
      alt="" width="100" height="150">

As far as I can see html-proofer does not support multiple URLs defined inside a srcset attribute.

See the draft spec here: http://w3c.github.io/html/semantics-embedded-content.html, and note srcset is already supported in the majority of modern browsers already: http://caniuse.com/#search=srcset

If support for this is something you think is worth including on html-proofer let me know and I'd be happy to work on it and make a pull request!

[fulldecent]

I'd like to see a device with 1.5x pixel density.

Yes, I think this is valid and in-scope for the project.

[ShoGinn]

I am still having problems with this and false errors with this srcset code:

<div class="w-100">
  <img alt="User::round" srcset="/project/user_400.webp 400w,
  /project/user_760.webp 760w, /project/user_1200x1200_fit_q75_h2_lanczos.webp
  1200w" src=/project/user_400.webp width="250" height="187" loading="lazy"
  data-zoomable>
</div>

* At public/project/index.html:7:
  internal image /project/user_400.webp 400w does not exist
* At public/project/index.html:7:
  internal image /project/user_760.webp 760w does not exist
* At public/project/index.html:7:
  internal image /project/user_1200x1200_fit_q75_h2_lanczos.webp 1200w does not exist

All the files there and operate normally.