Add @Preview to Falling Balls demo

examples/falling_balls/build.gradle.kts

@@ -6,7 +6,7 @@ plugins {
     // __KOTLIN_COMPOSE_VERSION__
     kotlin("jvm") version "1.5.10"
     // __LATEST_COMPOSE_RELEASE_VERSION__
-    id("org.jetbrains.compose") version "0.4.0"
+    id("org.jetbrains.compose") version "0.5.0-build229"
 }
 
 group = "me.user"
@@ -19,6 +19,7 @@ repositories {
 
 dependencies {
     implementation(compose.desktop.currentOs)
+    implementation(compose.uiTooling)
 }
 
 tasks.withType<KotlinCompile>() {

examples/falling_balls/src/main/kotlin/Game.kt

@@ -1,5 +1,6 @@
 package org.jetbrains.compose.demo.falling
 
+import androidx.compose.desktop.ui.tooling.preview.Preview
 import androidx.compose.foundation.layout.*
 import androidx.compose.material.Button
 import androidx.compose.material.Slider
@@ -72,6 +73,7 @@ class Game {
 }
 
 @Composable
+@Preview
 fun FallingBallsGame() {
     val game = remember { Game() }
     val density = LocalDensity.current