Allow notification to PgnViewerJS events

[mliebelt]

It would be nice to have the option to get notified when some event happens: like DOM events in the browser, but events triggered by the UI or the user. So the following events could be useful:

• moveMade
• pgnChanged
• fenChanged
• orientationChanged
• ...

I would be interested which kind of events are of any interest to the ones, that want to use PgnViewerJS as a library in their own application.

[mliebelt]

See https://stackoverflow.com/questions/15308371/custom-events-model-without-using-dom-events-in-javascript# for a nice short explanation how events can be integrated easily.

So one of the many proposals will be taken, so that at the end, the user of PgnViewerJS may register his event handlers by using something like (pseudo code):

let moveHandler = function (move) { ... here is your code ...}
let config = { moveMade: moveHandler, ...}
PGNV.pgnView('board', config)

[mliebelt]

I have asked ChatGPT, and the recommendations were:

• Use the native node.js built in event module, named EventEmitter. See the link for some documentation.
• Use the enhanced EventEmitter3, which is the more current implementation. See the link for the official source.