Update changelog in preparation for 7.4.0-rc3 (rojo-rbx#808)

Summarizes recent changes since 7.4.0-rc2 in the changelog

CHANGELOG.md

@@ -2,8 +2,16 @@
 
 ## Unreleased Changes
 * Changed `sourcemap --watch` to only generate the sourcemap when it's necessary ([#800])
+* Switched script source property getter and setter to `ScriptEditorService` methods ([#801])
+
+ 	This ensures that the script editor reflects any changes Rojo makes to a script while it is open in the script editor.
+
+* Fixed issues when handling `SecurityCapabilities` values ([#803], [#807])
 
 [#800]: https://github.com/rojo-rbx/rojo/pull/800
+[#801]: https://github.com/rojo-rbx/rojo/pull/801
+[#803]: https://github.com/rojo-rbx/rojo/pull/803
+[#807]: https://github.com/rojo-rbx/rojo/pull/807
 
 ## [7.4.0-rc2] - October 3, 2023
 * Fixed bug with parsing version for plugin validation ([#797])