splash.json — the animation the splash screen plays.

"Delivery Truck / Loading / Exporting" from LottieFiles:
https://lottiefiles.com/free-animation/delivery-truck-loading-exporting-Q2WoVTiHUy

500x500, 60fps, 235 frames (3.9s), eleven layers, pure vector with no embedded
images. Downloaded by hand — LottieFiles sits behind a Cloudflare challenge
that answers 403 to curl and to every fetch tool, so this file cannot be
refreshed by a script. If it needs replacing, use a browser.

Check the licence against that listing before a release. LottieFiles' free
animations are normally usable commercially with attribution, but that is worth
reading rather than assuming.

SplashScreen falls back to a built-in road loader when this file is absent, so
deleting it breaks nothing.