Added changelog note

CHANGELOG.md

@@ -1,7 +1,13 @@
 # Changelog for "d4science-keycloak-themes"
 
+All notable changes to this project will be documented in this file.
+This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
 ## [Unreleased]
-- First release (#19518)
+- First release 
+
+[#19518] Implemented the Keycloak "d4science" login parametric template.
+
+Each new gateway that does not implement its own specific login template should use by default this base "d4science" template. However, it is possible to set some parameters in `<keycloak_home>/themes/<gatewayname>/login/themes.properties` file to do some customizations such as logo, background, colors, and some links (see for example parameters of dev4.d4science.org and next.d4science.org themes).
 
 
-This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).