Image sharing service auto-upload plugin

[preaction]

It would be nice if we could automatically upload full-res images to photo sharing apps and hot-link from there. We would need to be able to check to see what images are already uploaded before uploading it again (probably using a content hash as an ID).

Services to look into:

• Google Photos
• Flickr
• Instagram
• Dropbox
• Apple iCloud?
• Git LFS (Github / custom site)

[preaction]

We should probably only do this during a deploy, so we may need to have an indicator of whether we're deploying or not. Which is kind of terrible (differences between build and deploy must be minimized to prevent surprises) and we may need a better way to think about it.