Geometry Nodes: new Is Viewport node

This node outputs true when geometry nodes is currently evaluated
for the viewport and false for final renders.

Ref T85277.

Differential Revision: https://developer.blender.org/D10302

release/scripts/startup/nodeitems_builtins.py

@@ -506,6 +506,7 @@ geometry_node_categories = [
         NodeItem("FunctionNodeRandomFloat"),
         NodeItem("ShaderNodeValue"),
         NodeItem("FunctionNodeInputVector"),
+        NodeItem("GeometryNodeIsViewport"),
     ]),
     GeometryNodeCategory("GEO_MESH", "Mesh", items=[
         NodeItem("GeometryNodeBoolean"),