fix default function escaping in readme

README.md

@@ -184,8 +184,8 @@ render("{{ even(42) }}", data); // true
 render("{{ divisibleBy(42, 7) }}", data); // true
 
 // Set default values if variables are not defined
-render("Hello {{ default(neighbour, "my friend") }}!"); // "Hello Peter!"
-render("Hello {{ default(colleague, "my friend") }}!"); // "Hello my friend!"
+render("Hello {{ default(neighbour, \"my friend\") }}!"); // "Hello Peter!"
+render("Hello {{ default(colleague, \"my friend\") }}!"); // "Hello my friend!"
 ```
 
 ### Callbacks