suppress output of asset copying in build script and adjust directory navigation

build.bat

@@ -0,0 +1,22 @@
+@echo off
+echo [1/4] Clearing old files...
+rd /s /q "out/app"
+
+echo [2/4] Building game...
+jpackage --type app-image ^
+  --dest "out/app" ^
+  --name "JGame2D" ^
+  --input "out/artifacts/JGame2D_jar" ^
+  --main-jar "JGame2D.jar" ^
+  --main-class de.miaurizius.jgame2d.core.Boot
+
+echo [3/4] Copy assets
+robocopy "assets" "out/app/JGame2D/assets" /e > nul
+
+echo [4/4] Zipping...
+cd out\app
+tar -a -c -f ..\JGame2D.zip JGame2D
+
+cd ../..
+
+echo Done!