[no ci] Add empty-columns section to the libcudf developer guide

cpp/doxygen/developer_guide/DEVELOPER_GUIDE.md

@@ -1483,6 +1483,17 @@ struct, and therefore `cudf::struct_view` is the data type of a `cudf::column` o
 
 `cudf::type_dispatcher` dispatches to the `struct_view` data type when invoked on a `STRUCT` column.
 
+# Empty Columns
+
+The libcudf columns support empty, typed content. These columns have no data and no validity mask.
+Empty strings or lists columns may or may not contain a child offsets column.
+It is undefined behavior (UB) to access the offsets child of an empty strings or lists column.
+Nested columns like lists and structs may require other children columns to provide the
+nested structure of the empty types.
+
+Use `cudf::make_empty_column()` to create fixed-width and strings columns.
+Use `cudf::empty_like()` to create an empty column from an existing `cudf::column_view`.
+
 # cuIO: file reading and writing
 
 cuIO is a component of libcudf that provides GPU-accelerated reading and writing of data file