Support for `AnnotationList`s

[cubap]

If you are interested, I announced Jack Reed's annotations from Slack on the Stanford Manifest (https://purl.stanford.edu/hg676jb4964/iiif/manifest) it was originally targeting. Currently, you only handle Ranges.

I may be bored later this week if you'd rather I pull request this.

[jeffreycwitt]

Supporting annotation list is definitely the next thing I want add. This way we can pull in transcriptions.

Let's do it.

I think there are some changes to be made to the plugin, since annotations apply to each canvas rather than the manifest, we either have to request all annotationsLists for the manifest at once and then only alert the user to their presence when they navigate to that canvas.

Or the plugin should be rechecking for notifications for each canvas.

[cubap]

I've never lifted the hood on Mirador myself, but I know smart people put it together, so I'll take an hour tomorrow and read up to see if I can spin this in for you.

The first, simple case, would use the same notification loader to get only those targeting the Manifest and load them into the otherContents instead of the structures. Best practice will need to be considered about transcription in general, since it may be more sensible to consider something like a Layer of annotations with a map of AnnotationLists keyed to canvas @ids. Mirador also probably has some considerations to make about some sort of viewing hint about on-screen display versus an index list in the side panel.