Added backward search example for less command

pages/common/less.md

@@ -16,10 +16,14 @@
 
 `g (start), G (end)`
 
-- Search for a string:
+- Forward search for a string:
 
 `/{{something}}   then   n (next), N (previous)`
 
+- Backward search for a string:
+
+`?{{something}}   then   n (next), N (previous)`
+
 - Exit:
 
 `q`