JS API feedback: Add Support for grouped "Unique value renderer"

[NicolasGIS]

Hello,

Just a feedback regarding JS API 4: I find it a pity that you don't support "grouped" values in your legend widget contrary to 3.X.

For example, a layer in MapViewer 3.X:

And in the new MapViewer using 4.X:

We now have to create and maintain a new field solely for visualization purpose: it's a pity !

Thanks for listening !

PS: otherwise  it's really cool, and fast, and the developper experience is awesome 🙂