Doc: Describe "Additional startup commands" in Run Settings

Update screenshots.

Task-number: QTCREATORBUG-26610
Change-Id: I9397edd4f050bf82da0cf2b49c8861bad4f00bab
Reviewed-by: hjk <hjk@qt.io>

doc/qtcreator/src/projects/creator-only/creator-projects-settings-run-debug.qdocinc

@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2021 The Qt Company Ltd.
+** Copyright (C) 2022 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the Qt Creator documentation.
@@ -38,6 +38,18 @@
     execute any JavaScript functions. Therefore, you must make sure that the
     port is properly protected by a firewall.
 
+    Optionally, in \uicontrol {Additional startup commands}, you can enter
+    additional settings for debugging C++:
+
+    \list
+        \li \l{Adding Custom Debugging Helpers}{Custom debugging helpers}
+        \li \l{Specifying GDB Settings}{GDB commands} to execute after GDB
+            has started, but before the debugged program is started or
+            attached, and before the debugging helpers are initialized
+    \endlist
+
+    However, you can usually leave this field empty.
+
     For more information about debugging, see \l{Debugging}.
 
 //! [run settings debugger]