Added example of using multiple params

examples/basic.exs

@@ -2,6 +2,8 @@ defmodule MyLib do
   use FFI.Library, name: "libstdc++.so.6"
 
   attach_function :puts, [:string], :int
+  attach_function :printf, [:string, :int], :int
 end
 
 MyLib.puts("Hello World from C stdlib")
+MyLib.printf("Random number: %d", :random.uniform(10))