adds recent updates to CHANGELOG.md

CHANGELOG.md

@@ -3,6 +3,9 @@ All notable changes to this project will be documented in this file.
 
 ## [unreleased] - [unreleased]
 - Defer reading salt from header until key derivation is triggered
+- Clarify usage of sqlite3_rekey for plaintext databases in header
+- Normalize attach behavior when key is not yet derived
+- Adds PRAGMA cipher_settings to query current database codec settings
 
 ## [4.0.1] - 2018-12-17
 - Based on upstream SQLite 3.26.0 (addresses SQLite “Magellan” issue)