Add application icon

src/main/kotlin/com/marvinelsen/willow/WillowApplication.kt

@@ -12,6 +12,7 @@ import com.marvinelsen.willow.ui.util.SearchService
 import javafx.application.Application
 import javafx.fxml.FXMLLoader
 import javafx.scene.Scene
+import javafx.scene.image.Image
 import javafx.scene.layout.BorderPane
 import javafx.scene.text.Font
 import javafx.stage.Stage
@@ -69,6 +70,7 @@ class WillowApplication : Application() {
             minWidth = WINDOW_MIN_WIDTH
             minHeight = WINDOW_MIN_HEIGHT
             scene = primaryScene
+            icons.add(Image(javaClass.getResourceAsStream("/img/icon.png")))
         }.show()
     }