Integrate LEL 2.0

[sagarpreet-chadha]

The integration process is written in the Readme : https://github.com/publiclab/leaflet-environmental-layers

The trick to have mapknitter layer ON by default is to exclude Mapknitter using the exclude param above and add Mapknitter using:

L.layerGroup.layerCode("mapknitter").addTo(mapID);

Thanks!