new one-liner for 'diff'

- signed-off-by: trimstray <trimstray@gmail.com>

README.md

@@ -1822,6 +1822,12 @@ ___
 diff <(cd directory1 && find | sort) <(cd directory2 && find | sort)
 ```
 
+###### Compare output of two commands
+
+```bash
+diff <(cat /etc/passwd) <(cut -f2 /etc/passwd)
+```
+
 ___
 
 ##### Tool: [tail](https://en.wikipedia.org/wiki/Tail_(Unix))