Add scrollbar actual implementation for js target

demo-common/src/jsMain/kotlin/com/seanproctor/datatable/demo/Scrollbar.ios.kt

@@ -0,0 +1,11 @@
+package com.seanproctor.datatable.demo
+
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Modifier
+import com.seanproctor.datatable.DataTableScrollState
+
+@Composable
+actual fun VerticalScrollbar(scrollState: DataTableScrollState, modifier: Modifier) {}
+
+@Composable
+actual fun HorizontalScrollbar(scrollState: DataTableScrollState, modifier: Modifier) {}