Update changelog

Author: bluss

CHANGELOG.md

@@ -1,8 +1,12 @@
 Recent Changes (arrayvec)
 =========================
 
-## Unreleased
+## 0.7.5
+
 - Add `as_ptr` and `as_mut_ptr` to `ArrayString` by @YuhanLiin
+- Add borsh serialization support by @honzasp and @Fuuzetsu
+- Move length field before before data in ArrayVec and ArrayString by @JakkuSakura
+- Fix miri error for ZST case in extend by @bluss
 
 ## 0.7.4