Add high fidelity audio and animations

## Overview

Currently the game is a prototype with simple graphics, no animations, and no audio. To make the game more polished, we would like to identify which assets need to be created and add those to the game.

The scope of this project is:
- [ ] Identify which assets should be created (consider both the current prototype and the levels being designed in #8 )
- [ ] Creation of audio assets
- [ ] Creation of visual assets
- [ ] Addition of all assets into Godot

NOTE: for anyone applying to this project through LFX Mentorship, please see https://github.com/knative-extensions/educational-game/issues/9#issuecomment-2637998623

Start by reviewing the current prototype and the levels being designed in issue #8, then identify the audio and visual assets needed. Create those assets and add all of them to the Godot game; the issue is done when every listed asset task is complete.

Written by the indexing model from the issue text.