Fix preview image not found for some sites

[Yarden-zamir]

Instead of grabbing the first link we itirate over the links and look for one of type image value.type.startsWith("image/"))
close #15

[brik0519]

Thanks for your commit
It works perfectly on my laptop

[Yarden-zamir]

This is still relevant and working well, anyone wanna merge it?

[dhamaniasad]

Thanks!