add readme

makefile

@@ -0,0 +1,14 @@
+PREFIX = /usr/local
+NAME = subs
+
+all:
+	@>&2 echo "Use 'make install'"
+
+install:
+	install -D -m 0755 ${NAME} ${PREFIX}/bin/${NAME}
+
+uninstall:
+	rm ${PREFIX}/bin/${NAME}
+
+test:
+	shellcheck -s sh ${NAME}