Add introduction.

shelf_with_drawers.scad

@@ -13,6 +13,9 @@
  *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+/* A shelf with cubical drawers. Units are supposed to be cm. The drawers begin
+ * 80cm above the ground. */
+
 $fa = 1;
 $fs = 0.2;