Create replay feature

[WhiteJP]

It would be useful to create a replay feature wherein we can replay a round to see what happened. This could be helpful for many reasons:

1. As researchers to get a quick understanding of what happened in a round.
2. To help with debugging/experiment development
3. Could even be interesting to show to other participants and get third party moral judgements of real behaviour

[WhiteJP]

A first version of this has been made. Many improvements still to be had, but the basic functionality is there. From the readme:

Preparation steps:

• run npm install to install Phaser and GridEngine in the directory
• npm run dev to serve it locally.
• in the app you will be prompted to enter the map name (a string), the original player states (json object), and the updates (an array of json objects). These can be found in CSV form after running empirica export in the empirica experiment directory (or cause that is buggy for me now can be taken directly the tajrica.json file of the experiment).

Gameplay:

• Space bar = pause
• right arrow = speed replay
• left arrow = slow replay