Geometry Nodes: add support for blackbody shader node

This adds the existing Blackbody shader node to geometry nodes, with the
same functionality.

Pull Request: https://projects.blender.org/blender/blender/pulls/114768

scripts/startup/bl_ui/node_add_menu_geometry.py

@@ -33,6 +33,7 @@ class NODE_MT_geometry_node_GEO_COLOR(Menu):
 
     def draw(self, _context):
         layout = self.layout
+        node_add_menu.add_node_type(layout, "ShaderNodeBlackbody")
         node_add_menu.add_node_type(layout, "ShaderNodeValToRGB")
         node_add_menu.add_node_type(layout, "ShaderNodeRGBCurve")
         layout.separator()