Add livewriting playback feature #8
Description
This is necessary to stop using video recordings during studies. In principle, we only need to be able to replay a file, either uploading it to the server or adding a script to load a page and load get it from the local system (although the former might be easier and preferred).
Ideally however, we should add more state tracking to the server to keep track of different studies and automatically load and reply desired submissions. This is definitely complex and should be out of scope for an initial implementation.
We should make sure to reuse the code that instantiates the editor and use the livewriting library to orchestrate the reply. However, we might need to conditionally turn off autocomplete features and live replay edits.
To start just create a new route 'replay' that loads a JSON file in the browser and replays it.