Update changelog

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project somewhat adheres to [Semantic Versioning](https://semver.org/sp
 The **"Breaking Changes"** listed below are changes that have been made in the decompilation projects (e.g. pokeemerald), which porymap requires in order to work properly. If porymap is used on a project that is not up-to-date with the breaking changes, then porymap will likely break or behave improperly.
 
 ## [Unreleased]
+### Added
+- Add ability to set the opacity of the scripting overlay.
+- Add ability to get/set map header properties via the API.
+
 ### Changed
 - If an object event is inanimate, it will always render using its first frame.
 - Only log "Unknown custom script function" when a registered script function is not present in any script.