chore: changelog for 0.19.4 (#600)

Author: tac0turtle

CHANGELOG.md

@@ -2,6 +2,11 @@
 
 ## Unreleased
 
+## 0.19.4 (October 28, 2022)
+
+- [#599](https://github.com/cosmos/iavl/pull/599) Populate ImmutableTree creation in copy function with missing field
+- [#589](https://github.com/cosmos/iavl/pull/589) Wrap `tree.addUnsavedRemoval()` with missing `if !tree.skipFastStorageUpgrade` statement
+
 ## 0.19.3 (October 8, 2022)
 
 - `ProofInner.Hash()` prevents both right and left from both being set. Only one is allowed to be set.