Add newsletter entry on main exit code

refs idaholab#28639

modules/doc/content/newsletter/2024/2024_09.md

@@ -7,6 +7,32 @@ for a complete description of all MOOSE changes.
 
 ## MOOSE Improvements
 
+### Exit Code Management
+
+The ability was added to allow an application to set its exit code, which can
+be seen in `MooseApp::setExitCode()`. This feature was added in order to better
+support instances in which you want to run an external process within an application,
+as the proper return code from the external process can be captured and
+returned via your application.
+
+In order for an application properly return this exit code, a modification is needed
+within the `main` function. To do this, modify the `main()` function in `src/main.C`
+to look like the following:
+
+```
+int
+main(int argc, char * argv[])
+{
+  return Moose::main<YourApp>(argc, argv);
+}
+```
+
+where `YourApp` is the class for your application.
+
+This change should be made as soon as possible as the logic that was changed here
+impacts the application command line options `--run` and `--copy-inputs` used for
+executing installed MOOSE applications.
+
 ## libMesh-level Changes
 
 ## PETSc-level Changes