Heatmap scalability

The heatmap plugin is not very scalable at the moment. For millions few data points, the map is "laggy" when moving the maps around (at a reasonable zoom level, when most of the data points are hidden).

From what I've investigated, it comes from the fact the, when the _redraw function is called, the code iterates over all data points to check if it is or not in the bounds of the map being shown.
It seems very inefficient since there exists data structure such as R-Tree that can efficiently retrieve the data points inside a box.

Now it seems that the Leaftlet.heat plugin is not maintained anymore (as noted in #1282 ). As far as I can tell, there is only the .min.js file on this repository, what are the plans for this plugin?
Host it completely on this organization so it can be modified and maintained?

For the problem of the performances, I wrote a quick POC using rbush and it improves the performance when we zoom on a specific area (and fewer points are actually shown on the map). I can contribute to this issue if necessary.

Inizia individuando il JavaScript minificato del plugin heatmap e il relativo percorso _redraw, quindi esamina la proof of concept rbush segnalata e le problematiche di manutenzione relative a Leaflet.heat. Il lavoro sarà considerato completato quando sarà stato concordato l'ambito di manutenzione del plugin e sarà dimostrato che la heatmap offre prestazioni migliori nel rendering di milioni di punti.