Fix typo in Compose Web tutorial

tutorials/Web/Style_Dsl/README.md

@@ -99,7 +99,7 @@ object AppStylesheet : StyleSheet() {
     }
     
     // A convenient way to create a class selector
-    // AppStylesheet.container can be used a class name in components
+    // AppStylesheet.container can be used as a class in component attrs
     val container by style {
         color("red")
         
@@ -158,4 +158,4 @@ object MyStyleSheet: StyleSheet() {
         backgroundColor(MyVariables.contentBackgroundColor.value(Color("#333")))
     }
 }
-```
\ No newline at end of file
+```