Add “;;; Commentary:” labels

pw-lib.el

@@ -17,6 +17,8 @@
 ;; You should have received a copy of the GNU General Public License
 ;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
+;;; Commentary:
+;;
 ;; Backend-independent library to access PipeWire functionality.
 ;; It abstracts data returned from `pw-access' methods and provides
 ;; functions to work with them.