Small update - Increased difficulty and level saving

I know it's only been a day since the last build, but I felt it was important to make some small changes/improvements. And I now have this nice build script, so it's super easy to generate a build!

I have added the ability to save the level that you get up to. So if you get up to level 3 then close the game, when you open it up again, you can start at level 3 again!

I've also increased the difficulty by adding some more enemies >:) This makes it harder to just walk through the level and get to the end without dying.