Exchange Annotator.JS with a still-maintained alternative

[tanius]

The Annotator.JS library and its plugins have the problem of being unmaintained since a few years. Due to this, we cannot even update from Annotator.JS 1.5 to 1.10, let alone 2.x (see #64).

So we probably want to switch out Annotator.JS with a piece of current software. @aerugo found RecogitoJS, which so far looks like a feature-complete replacement for Annotator.JS that is equally open source but still in active development. It supports tags, text annotations, replies to text annotations, and reportedly also image annotations.

[tanius]

Since a lot of other issues depend on whether we move forward with Annotator.JS or switch to a different library, this issue is relatively important.

[aerugo]

They are also developing Annotorious for image annotation. Maybe reaching out to Rainer Simon could be a good start to ask about his plans for it.