mention the code-switching

leaderboard.py

@@ -23,6 +23,10 @@ an [ISO 639-3 code](https://en.wikipedia.org/wiki/List_of_ISO_639-3_codes) (the
 an [ISO 15924](https://en.wikipedia.org/wiki/ISO_15924) code (the next 4 letters) for the writing system, 
 and optionally, a [Glottolog code](https://glottolog.org/) for the dialect.
 
+The varieties with a secondary language code (Egyptian Arabic, Colloquial Malay) use code-switching, 
+i.e. the speakers switch between the two languages (a colloquial and a standardized variety) 
+depending on the context (e.g. the formality level).
+
 For a fuller description of the languages and the codes used to represent them, please refer 
 to https://huggingface.co/datasets/facebook/bouquet#languages and the [BOUQuET paper](https://arxiv.org/abs/2502.04314).
 """