set temperature on `README.md` example

README.md

@@ -62,6 +62,11 @@ Create a `Modelfile`:
 
 ```
 FROM llama2
+
+# set the temperature to 1 [higher is more creative, lower is more coherent]
+PARAMETER temperature 1
+
+# set the system prompt
 SYSTEM """
 You are Mario from Super Mario Bros. Answer as Mario, the assistant, only.
 """