now project is multiplatform and correctly working

src/jsMain/kotlin/dev/inmo/jsuikit/modifiers/UIKitBackground.kt

@@ -0,0 +1,46 @@
+package dev.inmo.jsuikit.modifiers
+
+sealed class UIKitBackground(suffix: String) : UIKitModifier {
+    override val classes: Array<String> = arrayOf("uk-background-$suffix")
+
+    sealed class Color(suffix: String) : UIKitBackground(suffix) {
+        object Default : Color("default")
+        object Muted : Color("muted")
+        object Primary : Color("primary")
+        object Secondary : Color("secondary")
+    }
+
+    sealed class Size(suffix: String) : UIKitBackground(suffix) {
+        object Cover : Size("cover")
+        object Contain : Size("contain")
+        object FullWidth : Size("width-1-1")
+        object FullHeight : Size("height-1-1")
+    }
+
+    sealed class Position(suffix: String) : UIKitBackground(suffix) {
+
+        sealed class Top(suffix: String) : Position("top-$suffix") {
+            object Left : Top("left")
+            object Center : Top("center")
+            object Right : Top("right")
+        }
+
+        sealed class Center(suffix: String) : Position("center-$suffix") {
+            object Left : Position.Center("left")
+            object Center : Position.Center("center")
+            object Right : Position.Center("right")
+        }
+
+        sealed class Bottom(suffix: String) : Position("bottom-$suffix") {
+            object Left : Bottom("left")
+            object Center : Bottom("center")
+            object Right : Bottom("right")
+        }
+
+    }
+
+    object NoRepeat : Size("norepeat")
+
+    object Fixed : Size("fixed")
+
+}