update changelog

Author: PSeitz-dd

CHANGELOG.md

@@ -1,6 +1,8 @@
-0.8.1 (2025-09-30)
+0.9.0 (2025-09-30)
 ==================
 reexport `Number`
+Add a fmt::Display impl for Number https://github.com/PSeitz/serde_json_borrow/pull/39 (Thanks @quodlibetor)
+feat: Add get_key_value_at method for O(1) lookup in ObjectAsVec https://github.com/PSeitz/serde_json_borrow/pull/40  (Thanks @quodlibetor)
 
 0.8.0 (2025-06-15)
 ==================