feat(make): add make install/uninstall

Makefile

@@ -0,0 +1,13 @@
+PREFIX = /usr/local
+
+.PHONY: install
+
+install: $(PREFIX)/bin/sb3tosb2
+
+uninstall:
+	rm -f $(PREFIX)/bin/sb3tosb2
+
+$(PREFIX)/bin/sb3tosb2: sb3tosb2.py
+	echo "#!/usr/bin/env python3" > $@
+	cat $< >> $@
+	chmod +x $@

README.md

@@ -11,6 +11,15 @@ Installation
 --------------
 Download and extract the ZIP file and move the sb3tosb2.py file to wherever you want.
 
+or:
+
+```bash
+sudo make install
+```
+
+to install it to `/usr/local/bin/sb3tosb2`
+(also adds a shebang for it to run with python3).
+
 Usage
 --------------
 1. Run sb3tosb2.py with Python
@@ -47,4 +56,4 @@ Known Issues
 - Compatibility mode changes variable monitor labels
 - Compatibility mode allows ([ v] of [ v]) to access only variables (not attributes like x position, backdrop #, etc.)
 - Dragging in projects converted with compatibility mode does not have the same pen behavior as in 3.0
-- Unlimited join does not check case when checking string equality
+- Unlimited join does not check case when checking string equality