Adds Warning Dialog When Following an External Link in Project Manager (#6003)

Signed-off-by: Alex Peterson <26804013+AMZN-alexpete@users.noreply.github.com>

Code/Tools/ProjectManager/Source/ProjectManagerSettings.cpp

@@ -6,7 +6,7 @@
  *
  */
 
-#include "ProjectManagerSettings.h"
+#include <ProjectManagerSettings.h>
 
 #include <AzCore/Settings/SettingsRegistryMergeUtils.h>
 #include <AzCore/IO/ByteContainerStream.h>
@@ -51,4 +51,9 @@ namespace O3DE::ProjectManager
     {
         return QString("%1/Projects/%2/BuiltSuccessfully").arg(ProjectManagerKeyPrefix).arg(projectName);
     }
+
+    QString GetExternalLinkWarningKey()
+    {
+        return QString("%1/SkipExternalLinkWarning").arg(ProjectManagerKeyPrefix);
+    }
 }