validate image links

[yeo-yeo]

It looks like some people have been lazy when adding dogs to the API and not submitted proper image links, which leads to some broken images on the home page. If you really want to give yourself a challenge, perhaps you could dream up a way to validate the dog's image property you get back from the API and only show the card if you think it checks out!

e.g.
✅ http://www.imagesite.com/dogimage.jpg
❌ asdffghjjkk