Add support for as_leaflet_layer in Map.add

[banesullivan]

I use ipyleaflet a ton with localtileserver and I was thinking it'd be convenient if ipyleaflet.Map's add() method supported passing objects with an as_leaflet_layer() interface.

There may be better/cleaner ways to do this, so suggestions are welcome! But, my end goal is to make it easier to go from raster file path to ipyleaflet.Map showing tiles like:

from localtileserver import TileClient
from ipyleaflet import Map

client = TileClient('path/to/geo.tif')  # <--- will have `as_leaflet_layer` method

m = Map(center=client.center(), zoom=client.default_zoom)
m.add_layer(client)
m

[davidbrochart]

Thanks for the suggestion @banesullivan, I think it would make sense, including for xarray-leaflet.

[martinRenou]

Thank you!

[davidbrochart]

@banesullivan I think we should document this interface.

[banesullivan]

I think we should document this interface.

Agreed. If you all are happy with as_leaflet_layer being the name and it being a method, then I'll add some docs when I get a few minutes

[banesullivan]

@davidbrochart and @martinRenou, please review this explanation and feel free to modify. This is what I came up with on a whim to document the interface.

[davidbrochart]

@banesullivan I just made a small change to the docs, otherwise it looks good to me.
Thanks!

[banesullivan]

Thank you for the second set of eyes and improvements!

[banesullivan]

Hm. I just checked the docs built from master: https://ipyleaflet.readthedocs.io/en/master/layers/layer_like.html

and it looks like the data are not embedded in the jupyter output

[davidbrochart]

I opened #1037, the code was in LayerGroup instead of Map 😄