copy avif dlls into win distribution

lazpaint/release/windows/stage.bat

@@ -24,6 +24,7 @@ if not exist lazpaint32 mkdir lazpaint32
 copy ..\bin\lazpaint32.exe lazpaint32\lazpaint.exe >nul
 copy dcraw\dcraw32.exe lazpaint32\dcraw.exe >nul
 copy libwebp\libwebp32.dll lazpaint32 >nul
+if exist libavif\win32 copy libavif\win32\*.dll lazpaint32 >nul
 copy ..\bin\readme.txt lazpaint32 >nul
 copy ..\bin\*.ini lazpaint32 >nul
 if not exist lazpaint32\i18n mkdir lazpaint32\i18n
@@ -47,6 +48,7 @@ if not exist lazpaint64 mkdir lazpaint64
 copy ..\bin\lazpaint64.exe lazpaint64\lazpaint.exe >nul
 copy dcraw\dcraw64.exe lazpaint64\dcraw.exe >nul
 copy libwebp\libwebp64.dll lazpaint64 >nul
+if exist libavif\win64 copy libavif\win64\*.dll lazpaint64 >nul
 copy ..\bin\readme.txt lazpaint64 >nul
 copy ..\bin\*.ini lazpaint64 >nul
 if not exist lazpaint64\i18n mkdir lazpaint64\i18n