add release notes for EasyBuild v4.8.1

Author: boegel

docs/changelog-docs.md

@@ -7,6 +7,9 @@ search:
 
 (for EasyBuild release notes, see [EasyBuild release notes][release_notes])
 
+- **release 20230911.01** (*9 Sept 2023*): update
+    release notes for EasyBuild v4.8.1 (see
+    [EasyBuild v4.8.1 (11 Sept 2023)][release_notes_eb481])
 - **release 20230707.01** (*7 July 2023*): update
     release notes for EasyBuild v4.8.0 (see
     [EasyBuild v4.8.0 (7 July 2023)][release_notes_eb480])