Add Liber Usualis images to repository

[CThierrin]

Resolves issue #19
Also update Readme to better explain the images

[dchiller]

@CThierrin I can't review the files because there are too many/they are too large. I assume they are mostly the image files?

I'm ok with this as long as we also put the images in Arbutus Object Storage, which is where we've historically added image files. There are instructions for this in the wiki.

[CThierrin]

@CThierrin I can't review the files because there are too many/they are too large. I assume they are mostly the image files?

I'm ok with this as long as we also put the images in Arbutus Object Storage, which is where we've historically added image files. There are instructions for this in the wiki.

They are indeed image files. I'll look into adding the images to Arbutus

[dchiller]

Ok, I literally can't add a review, so you can consider this comment my "approval".