feat: Add sealed classes example to client code

The code changes in this commit add a new file `Sealed.scala` to the `examples/client/src/main/scala/samples` directory. This file contains an example of using sealed classes in Scala. It defines a sealed trait `Animal` and two case classes `Horse` and `Lama` that extend the `Animal` trait. It also includes a case class `Owner` that has a `name` and a `pet` field of type `Animal`. The commit also updates the `HelloWorld.scala` file to include the new `sealedClasses` sample component.

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

examples/client/src/main/scala/HelloWorld.scala

@@ -17,6 +17,7 @@ object App extends App {
 
   private val demos = Seq(
     samples.simple,
+    samples.sealedClasses,
     samples.either,
     samples.enums,
     samples.person,

examples/client/src/main/scala/samples/Sealed.scala

@@ -0,0 +1,29 @@
+package samples
+
+import dev.cheleb.scalamigen.{*, given}
+
+import com.raquo.laminar.api.L.*
+
+import com.raquo.airstream.state.Var
+
+sealed trait Animal
+case class Horse(name: String, age: Int) extends Animal
+case class Lama(name: String, age: Int, splitDistance: Int) extends Animal
+
+case class Owner(name: String, pet: Animal)
+
+val sealedClasses = Sample(
+  "Sealed", {
+
+    val eitherVar = Var(Owner("Agnes", Horse("Scala le chat", 6)))
+
+    div(
+      child <-- eitherVar.signal.map { item =>
+        div(
+          s"$item"
+        )
+      },
+      eitherVar.asForm
+    )
+  }
+)

examples/client/src/main/scala/samples/Tree.scala

@@ -17,7 +17,8 @@ object Tree:
       case (Empty, Node(_, _, _)) => false
       case (Node(_, left1, right1), Node(_, left2, right2)) =>
         isSameStructure(left1, left2) && isSameStructure(right1, right2)
-implicit def treeInstance[A](using
+
+given treeInstance[A](using
     default: Defaultable[A]
 )(using Form[A]): Form[Tree[A]] =
   new Form[Tree[A]] { self =>