update docs regarding undefined behavior when using multiple z_bytes_…

…writers

include/zenoh-pico/api/primitives.h

@@ -1055,7 +1055,8 @@ int64_t z_bytes_reader_tell(z_bytes_reader_t *reader);
 
 /**
  * Constructs writer for :c:type:`z_loaned_bytes_t`.
- *
+ * Note: creating another writer while previous one is still in use is undefined behaviour.
+ * 
  * Parameters:
  *   bytes: Data container to write to.
  *   writer: Uninitialized memory location where writer is to be constructed.