add help docs and ?

docs/nodes/Folder.md

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+# Folder
+
+Pick a folder and output its directory path plus one file socket per compatible file inside it. Supported files include common images, .npy/.npz arrays, and .gwy/.sxm/.ibw scans.
+
+## Inputs
+
+None.
+
+## Outputs
+
+| Name | Type | Description |
+|------|------|-------------|
+| directory | DIRECTORY | The selected folder path |
+
+## Controls
+
+| Name | Type | Default | Description |
+|------|------|---------|-------------|
+| folder | FOLDER_PICKER | "" | Path to the folder to list |
+
+## Limitations
+
+- Only files with supported extensions are listed; subdirectories and unsupported file types are ignored.
+- The number of file output sockets is determined at load time by the folder contents.