Schema: Add basic folder schema (#67561)

kinds/folder/folder_kind.cue

@@ -0,0 +1,30 @@
+package kind
+
+name:        "Folder"
+maturity:    "merged"
+description: "A folder is a collection of resources that are grouped together and can share permissions."
+
+lineage: seqs: [
+	{
+		schemas: [
+			//0.0
+			{
+
+				spec: {
+					// Unique folder id. (will be k8s name)
+					uid: string
+
+					// Folder title
+					title: string
+
+					// Description of the folder.
+					description?: string
+				} @cuetsy(kind="interface")
+				//
+				// TODO: 
+				// common metadata will soon support setting the parent folder in the metadata
+				//
+			},
+		]
+	},
+]