Add a StyleScope.padding placeholder and update the demo code

Author: ShreckYe

compose-multiplatform-common/src/commonMain/kotlin/com/huanshankeji/compose/ui/ModifierOrAttrsScope.kt

@@ -15,6 +15,15 @@ expect class StyleScope {
     fun margin(value: SizeValue)
 }
 
+private const val PADDING_MESSAGE =
+    "This function is a placeholder for code completion. " +
+            "Use `margin` to add space around the composable, which is equivalent to `Modifier.padding`. " +
+            "Set `margin` in the inner composable to add inner padding."
+
+@Deprecated(PADDING_MESSAGE)
+fun StyleScope.padding(value: SizeValue): Unit =
+    throw NotImplementedError(PADDING_MESSAGE)
+
 /*
 /** An alternative immutable design like [Modifier]. */
 expect class ModifierOrAttrsImmutable<T : Element> {

demo/src/commonMain/kotlin/com/huanshankeji/compose/material/demo/Composables.kt

@@ -24,7 +24,11 @@ fun App() {
                 margin(16.dpOrPx)
             }
         }) {
-            Column {
+            Column({
+                style {
+                    margin(16.dpOrPx)
+                }
+            }) {
                 BasicText("basic text")
                 Text("Material text")