add a script for building an executable zip file

see https://docs.python.org/3/library/zipapp.html

build.sh

@@ -0,0 +1,22 @@
+#!/bin/bash
+set -eu
+
+mkdir -p myapp
+
+if ! test -d myapp/bps; then
+	echo "Installing dependencies to ./myapp"
+	pip install -r requirements.txt --target myapp
+	rm -rf myapp/bin/ myapp/bps/test/ myapp/{bps,PySimpleGUI}/__pycache__/ myapp/*.dist-info/
+fi
+
+echo "Copying source files to ./myapp"
+cp Fusion_Graph.py myapp/Fusion_Graph.py
+cp Fusion_Items.py myapp/Fusion_Items.py
+cp Randomizer.py myapp/Randomizer.py
+cp GUI.py myapp/GUI.py
+cp MFOR.py myapp/__main__.py
+
+echo "Building MFOR.pyz"
+python3 -m zipapp -o MFOR.pyz --python "/usr/bin/env python3" --compress myapp
+
+echo "Done"