Image duplication for screen resize (#401)

## Link to GitHub Issue, if one exists
#399 

## Description of change
Add image duplication option to screen resize, allowing overflow images
to wrap around the other side.

## Testing
Tested with DDR, IIDX (windowed and full screen TDJ), SDVX (orientation
swap)

src/spice2x/overlay/windows/screen_resize.cpp

@@ -55,6 +55,7 @@ namespace overlay::windows {
             scene.offset_y = 0;
             scene.scale_x = 1.f;
             scene.scale_y = 1.f;
+            scene.duplicate = cfg::ScreenDuplicateMode::None;
         }
 
         cfg::SCREENRESIZE->enable_window_resize = false;
@@ -149,6 +150,17 @@ namespace overlay::windows {
             ImGui::HelpMarker("Hint: ctrl + click on the slider to type in a numeric value.");
         }
 
+        static const char* dupe_items[] = { "None", "Copy Left", "Copy Right" };
+        ImGui::Combo(
+            "Duplicate",
+            reinterpret_cast<int *>(&scene.duplicate),
+            dupe_items,
+            ARRAYSIZE(dupe_items));
+        ImGui::SameLine();
+        ImGui::HelpMarker(
+            "Show an identical copy of the image on the left or right, allowing you to achieve "
+            "wrap-around effect when an offset is set.");
+
         ImGui::EndDisabled();
     }