fix: geojson layers pmIgnore

[lopezvoliver]

Similar to #1249 , this PR updates jupyter_leaflet so that individual layers created by the LeafletGeoJSONModel get the proper pmIgnore option -- and disable the pm if it's already attached. This fixes the issue that Geoman is able to edit GeoJson layers, even though they inherit the pm_ignore from the base Layer class.

[mangecoeur]

There's probably overlap with this PR #1247

[lopezvoliver]

There's probably overlap with this PR #1247

Hey @mangecoeur, I tested an environment with PR #1247 and Geoman was still able to modify GeoJSON layers:

I think the important part of this PR that solves this issue is this:

            if (pmIgnore && layer.pm) {
              layer.pm.disable();
              delete (layer as any).pm;
            }

[mangecoeur]

Thanks, actually for my current use i mashed together both my current PR and your fixes into a kind of frakenpackage because I couldn't wait for a new ipyleaflet release. Would really like to land all of these fixes in the main repo instead.

See the branch here (https://github.com/mangecoeur/ipyleaflet/tree/merge_extra_geoman_prs) I was actually in such a rush that I just copy-pasted your file changes rather than merge from your branch 😅. Would rather re-do it clean instead.

[lopezvoliver]

Same 😅 -- I have a custom mix and match of recent fixes. Hopefully the maintainers have some time to review these soon 👀