Add new PNG images for clean and preview outputs

- Added `image_clean.png` to the output directory for the clean image representation.
- Added `image_clean_preview.png` for the preview of the clean image.
- Introduced `image_svg_clean.png` for the SVG clean image representation.

packaging/appimage/AppRun

@@ -0,0 +1,25 @@
+#!/bin/sh
+set -eu
+
+APPDIR=$(CDPATH= cd -- "$(dirname -- "$0")" && pwd)
+VENV_DIR="$APPDIR/usr/opt/python"
+GAME_DIR="$APPDIR/usr/share/mice"
+
+if [ -n "${MICE_DATA_DIR:-}" ]; then
+    DATA_DIR="$MICE_DATA_DIR"
+elif [ -n "${XDG_DATA_HOME:-}" ]; then
+    DATA_DIR="$XDG_DATA_HOME/mice"
+else
+    DATA_DIR="$HOME/.local/share/mice"
+fi
+
+mkdir -p "$DATA_DIR"
+
+export PATH="$VENV_DIR/bin:${PATH:-}"
+export LD_LIBRARY_PATH="$APPDIR/usr/lib${LD_LIBRARY_PATH:+:$LD_LIBRARY_PATH}"
+export MICE_PROJECT_ROOT="$GAME_DIR"
+export MICE_DATA_DIR="$DATA_DIR"
+export PYTHONNOUSERSITE=1
+
+cd "$GAME_DIR"
+exec "$VENV_DIR/bin/python" rats.py "$@"

packaging/appimage/mice.desktop

@@ -0,0 +1,9 @@
+[Desktop Entry]
+Type=Application
+Name=Mice!
+Comment=Strategic rat extermination game built with Python and SDL2
+Exec=mice
+Icon=mice
+Categories=Game;StrategyGame;
+Terminal=false
+StartupNotify=false