Add utils for str8 printing

src/core/strings/str8/str8.h

@@ -17,6 +17,10 @@ struct str8 {
 
 typedef const Str8 Str8RO;
 
+// Utilities to be used with printf functions
+#define WAPP_STR8_SPEC "%.*s"
+#define wapp_str8_varg(STRING) (int)STRING.size, STRING.buf
+
 #define wapp_str8_buf(CAPACITY) ((Str8){.capacity = CAPACITY, .size = 0, .buf = (c8[CAPACITY]){0}})
 
 // Utilises the fact that memcpy returns pointer to dest buffer and that getting