[UX Map] Rename a variable

[javiereguiluz]

When using UX Map and Leaflet bridge to customize a marker, you have to do this:

const { definition, leaflet } = event.detail;
// ...

As suggested by @Kocal, the leaflet variable should probably be named L because Leaflet uses L in all its docs. Now that the bridge is so new (and experimental), we could even rename the variable wihout considering BC, etc.

Thanks

[Kocal]

I can work on it tomorrow at noon