Feature Proposal: Viewer - Point Annotation - Option to keep point size consistent despite zoom level

[joseph-bayer]

The IIIF cookbook mentions in the last sentence of "Implementation notes" that "Viewers might consider implementing scale-independent point markers so that they are visible at every level of zoom".

I've found the place in the code where annotation are being added, however I'd need to do some research into how to keep the point the same size despite zoom level.

I propose that we update the config to have an "annotations" object for various annoation-related options and add a prop to that object to support this.

If this sounds like a good idea to you, I'd love to implement this. If you have any thoughts off the top of your head regarding implementation, let me know!