chore: add CHANGELOG

Author: nytamin

CHANGELOG.md

@@ -0,0 +1,16 @@
+# Changelog
+
+This log lists changes between versions.
+
+
+
+
+## Version 1 - Draft 0
+
+This is a draft for Version 1. During its development, it may contain breaking changes.
+
+The log below details the changes during development of this version:
+
+* 2025-03-27: Draft 0 made public.
+* 2025-04-23: Fix in JSON-schemas: Changed `main` property in Graphics manifest to be **mandatory**.
+  (Before, it was defined as mandatory in the specification document, but not in the JSON-schemas.)

README.md

@@ -15,6 +15,8 @@ EBU members as well as the general industry is invited to join the [HTML Graphic
 
 Feedback can also be submitted using [GitHub Issues](https://github.com/ebu/ograf/issues).
 
+Graphics and Render system developers are encouraged to follow changes in the [Changelog](./CHANGELOG.md).
+
 ### Time plan
 
 - April 2025: