Allow users to set preserveDrawingBuffer in the options

[sheeley820]

It was discovered that printing maps rendered with esri-leaflet-vector does not work in Firefox.

An issue was created here.

This PR fixes that issue by allowing the user to set preserveDrawingBuffer to true, which resolves the issue. It is set to false by default in the maplibre-gl-js project in the scr/ui/map.ts file for performance optimizations. Adding the ability for a user to toggle this value through esri-leaflet-vector, but maintaining a default of false will help users who want to provide printing capabilities, while maintaining the performance optimization for those who do not have this need.

[gavinr-maps]

Thank you for the PR.

If we Expose the MaplibreGLJSLayer Variable (#197), this PR #199 is not needed, correct? Because you could modify the preserveDrawingBuffer property on the exposed MaplibreGLJSLayer Variable.

[sheeley820]

@gavinr-maps So technically it is possible to do the following even without MaplibreGLJSLayer being exposed:

const vector = L.esri.Vector.vectorBasemapLayer(basemapEnum, {
        apiKey: apiKey
    })
vector.options.preserveDrawingBuffer = true
vector.addTo(map)

And this resolves the printing error, but for me it seems like since we already allow MapLibre options to be passed directly into the VectorTileLayer initialization (pane, opacity) it would make sense to allow perserveDrawingBuffer to be passed in through the VectorBasemapLayer and VectorTileLayer constructors as well.

[gavinr-maps]

Looks good. In the future if people need access to more options, we should introduce a mapLibreMapOptions property. But we can avoid prematurely optimizing by just going with this for now.

[gavinr-maps]

This was released in v4.2.0.