fix merge docs on how to report strand with . Thanks to @balwierz.

docs/content/tools/merge.rst

@@ -113,9 +113,17 @@ The ``-s`` option will only merge intervals that are overlapping/bookended
   chr1  501  1000  a4  4 +
 
   $ bedtools merge -i A.bed -s
-  chr1  100  250    +
-  chr1  501  1000   +
-  chr1  250  500    -
+  chr1  100  250
+  chr1  501  1000
+  chr1  250  500
+
+To also report the strand, you could use the ``-c`` and ``-o`` operators (see below for more details):
+
+.. code-block:: bash
+
+  $ bedtools merge -i A.bed -s -c 6 -o distinct
+  chr1  100 250 +
+  chr1  501 1000  +
 
 ==========================================================================
 ``-S`` Reporting merged intervals on a specific strand.