Add support for Leaflet 1.1.0+

[rkatka]

Leaflet version 1.1.0 added ES6 and Rollup that made all leaflet objects non-extendable. This results in the current version of Leaflet.markercluster (1.1.0) no longer being compatible with the latest versions of Leaflet.

[danzel]

Ah dumb.
I think there is a plugin upgrade somewhere? Someone wanna find and link it please.
I'm pretty busy with other things ATM, so hoping someone else can pick this up. 🙏

[ghybs]

Hi @rkatka,

While you are absolutely right that Leaflet 1.1.0 introduced a compatibility bug for plugins that need to extend some base objects (like L.Util and L.DomUtil), I do not recall such extension requirements in Leaflet.markercluster?

A quick test shows no particular issue: (Leaflet 1.1.0 + Leaflet.markercluster 1.1.0)
https://plnkr.co/edit/4xjaKXfBk6AnSY0Q388w?p=preview

That being said, if you can just upgrade to Leaflet 1.2.0, the above mentioned bug has been resolved.

[danzel]

This has been fixed since.