Create bugfix flag to enable system dialog transitions in Desktop Mode.

Bug: 335638193
Change-Id: Id1ce747eda197ea465a82642c56ec7fd82d08bf9
Test: NA
Flag: EXEMPT adding flag
diff --git a/core/java/android/window/flags/lse_desktop_experience.aconfig b/core/java/android/window/flags/lse_desktop_experience.aconfig
index d39ecab..f474b34 100644
--- a/core/java/android/window/flags/lse_desktop_experience.aconfig
+++ b/core/java/android/window/flags/lse_desktop_experience.aconfig
@@ -353,6 +353,16 @@
 }
 
 flag {
+    name: "enable_desktop_system_dialogs_transitions"
+    namespace: "lse_desktop_experience"
+    description: "Enables custom transitions for system dialogs in Desktop Mode."
+    bug: "335638193"
+    metadata {
+        purpose: PURPOSE_BUGFIX
+    }
+}
+
+flag {
     name: "enable_move_to_next_display_shortcut"
     namespace: "lse_desktop_experience"
     description: "Add new keyboard shortcut of moving a task into next display"