README.md: use buffer source for / and ? (#1186)

README.md

@@ -102,13 +102,15 @@ lua <<EOF
     })
   })
 
-  -- Use buffer source for `/` (if you enabled `native_menu`, this won't work anymore).
-  cmp.setup.cmdline('/', {
+  -- Use buffer source for `/` and `?` (if you enabled `native_menu`, this won't work anymore).
+  for _,v in pairs({ '/', '?' })
+    cmp.setup.cmdline(v, {
       mapping = cmp.mapping.preset.cmdline(),
       sources = {
         { name = 'buffer' }
       }
     })
+  end
 
   -- Use cmdline & path source for ':' (if you enabled `native_menu`, this won't work anymore).
   cmp.setup.cmdline(':', {