DOC: Added CITATION.cff to the list of files in the release guide where the...

DOC: Added CITATION.cff to the list of files in the release guide where the version number must be updated

RELEASE_GUIDELINES.md

@@ -22,6 +22,7 @@ guidelines of the CaosDB Project
   * [pom.xml](./pom.xml) (probably this means to remove the `-SNAPSHOT`)
   * `src/doc/conf.py`
   * `CHANGELOG.md`
+  * `CITATION.cff` (update version and date)
 
 5. Merge the release branch into the main branch.