feat(TileLayer): add hide skirt parameter

[AnthonyGlt]

Description

Add a new parameter "hideSkirt" to the layer to hide the skirt (borders of tiles).

To test, the parameter can be updated like this -> view.tileLayer.hideSkirt = true;

Motivation and Context

Useful when the opacity < 1

Screenshots (if appropriate)

With hideSkirt = false (current default behavior)

with hideSkirt = true

Important

If merged, it's necessary to update the doc to describe this parameter and how to use it

[jailln]

I think we should hide it by default when changing the opacity of the layer to always avoid the effect you show in the first screenshot; WDYT @AnthonyGlt @Desplandis ?

[AnthonyGlt]

if we hide it, we see through the terrain , cf screen shot below.

To correct this, it's necessary to switch the scene background color to black and disable the atmosphere

[jailln]

I meant hide it only when the opacity is < 1

[AnthonyGlt]

the result will be nice when we don't zoom but when we zoom, we'll see the background color (like the screenshot above), can be a trade off.

[jailln]

the result will be nice when we don't zoom but when we zoom, we'll see the background color (like the screenshot above), can be a trade off.

Yes you're right, I'm not sure what's best so let's leave it like this for now

[AnthonyGlt]

Linked proposal for future development of underground visualization https://github.com/iTowns/itowns/issues/2281