fix(vkontakte): update photo detection

[hgrsd]

Photo scraping doesn't currently work for VKontakte, because data-photo-id seems no longer included in the anchor's attributes.

There is, however, and aria-label that starts with photo included in the attributes; we can use that to detect whether we are dealing with a photo. Doing so allows the existing logic to scrape the URLs again :).

This should close #471.

[hgrsd]

@JustAnotherArchivist I took a stab at closing this issue - let me know what you think :)

[JustAnotherArchivist]

Thanks a lot, and apologies for the delay!