Add more arithmetic examples

VL1/content/VL1_arithmetic_and_co.tex

@@ -4,5 +4,6 @@
 > 6 * 5.0
 > "Hello" ++ " world"
 > "Haskell" > "C++"
+> 3 > 4
 > True && False
 \end{haskellcode*}