Docs: Specify that src will reference to the first declared size

[edgarshurtado]

Hi,

I'd like to contribute to improving the documentation for this great plugin.

It's only a detail but I haven't been able to find in the docs that if some sizes are set like [300, 600, 1200], the first one will be the one used for src attribute. So in my case, IE was using the 300px image instead of the bigger one. To fix this I had just to put 1200 as the first array element.

Could this be added to the docs?

Thank you!

[edgarshurtado]

I've just realized that, by doing so, it totally breaks srcset...

There's any way to specify this?

Thank you!