Improve makefile and readme

Makefile

@@ -4,10 +4,20 @@ LIBS = -lrlottie
 DEPS = lodepng.cpp
 TARGET = lfe
 
+ifeq ($(PREFIX),)
+    PREFIX := /usr/local
+endif
+
 all: $(TARGET)
 
 $(TARGET): $(TARGET).cpp
-	$(CC) $(CFLAGS) -o $(TARGET) $(DEPS) $(TARGET).cpp $(LIBS)
+    $(CC) $(CFLAGS) -o $(TARGET) $(DEPS) $(TARGET).cpp $(LIBS)
+
+install: $(TARGET)
+    install -m 644 $(TARGET) $(DESTDIR)$(PREFIX)/bin/
+
+uninstall:
+    rm -f $(DESTDIR)$(PREFIX)/bin/$(TARGET)
 
 clean:
-	$(RM) $(TARGET)
+    $(RM) $(TARGET)