Update background-mode.md

Added new include ZABAPGIT_BACKGROUND_USER_EXIT to API note.

Author: gardian12

src/user-guide/repo-settings/background-mode.md

@@ -47,3 +47,6 @@ If credentials are required for accessing the repository, you will have to maint
 ### Custom background modes
 
 Implement interface `ZIF_ABAPGIT_BACKGROUND` in a global class, and it will automatically show up in the abapGit background settings, making it possible to configure and run for a repository.
+While using the standalone version of abapGit implement the include `ZABAPGIT_BACKGROUND_USER_EXIT`.
+Both ways of adding a plugin can exist in parallel, but due to the restrictions of dynamic method calls global classes are available by the developer version only. Same is true for include based implementations. These are execute by the standalone version only.
+