Add doc for List type definition

src/places.ts

@@ -55,6 +55,19 @@ const listSchema = {
   required: ['id', 'title', 'placeRefs', 'createdAt'],
 } as const;
 
+/**
+ * Represents a List object.
+ *
+ * Core properties enforced by schema:
+ * - `id`: Unique identifier (slug)
+ * - `title`: Human readable title
+ * - `placeRefs`: Array of place references containing `id` and `geohash`
+ * - `createdAt`: ISO date string
+ *
+ * Optional properties:
+ * - `color`: Hex color code
+ * - `updatedAt`: ISO date string
+ */
 export type List = FromSchema<typeof listSchema> & { [key: string]: any };
 
 /**