Update index.md

Signed-off-by: Matt-RUN-CKB <matt@nervos.community>

what_are_bitcoin_covenants_(explainCKBot)/index.md

@@ -1,7 +1,7 @@
 ---
 title: 'What are Bitcoin Covenants?'
 coverImage: 'images/image1.png'
-category:
+category: Bitcoin
 subtitle: 'Bitcoin covenants are a proposed method for adding additional constraints to the ways Bitcoin can be spent, beyond the standard conditions imposed by Bitcoin's scripting language.'
 date: '2024-08-21 T20:00:00.000Z'
 author: