Geometry Nodes: Group Input String Socket: Add "Attribute List" Subtype Option

All of the named attribute nodes use a string socket for name input.

If properly connected to the tree, clicking in the string socket's entry field will pop up a list of available named attributes. Which is pretty great.

But connect the same String socket to a group input node and that ability is lost, because Group Input String sockets only have 2 Subtypes, "None" and "File Path"

This addition would make using named attributes in node groups much easier. Especially with node groups that you want to be reusable assets.