Make the first text field in the Material 3 demo readonly to show that the pointer shows as an I-beam

Author: ShreckYe

demo/src/commonMain/kotlin/com/huanshankeji/compose/material/demo/Material3.kt

@@ -115,6 +115,7 @@ fun Material3(/*modifier: Modifier = Modifier*/) {
         TextFieldWithMaterialIcons(
             text,
             { text = it },
+            readOnly = true,
             label = label,
             placeholder = placeholder,
             leadingIcon = Icons.Default.Add,