support multi-resolution images in disabled icons on Java 9+ (e.g. @2x icons on macOS) (issue #70)

flatlaf-demo/build.gradle.kts

@@ -43,6 +43,9 @@ tasks {
 
 		manifest {
 			attributes( "Main-Class" to "com.formdev.flatlaf.demo.FlatLafDemo" )
+
+			if( JavaVersion.current() >= JavaVersion.VERSION_1_9 )
+				attributes( "Multi-Release" to "true" )
 		}
 
 		exclude( "module-info.class" )