Lava and level size

Changes in this update:

• Lava has been added! Use it as a hazard; anyone who touches it will be placed back at the start of the level as if they'd fallen out of the screen.
• Level size limit removed.
  • You can now extend your levels beyond the scope of a single screen.
  • Note: the level editor will attempt to shrink your levels down as much as possible when you return to play mode. Your level may shrink in an unwanted way because of this. The fix is to ensure you have a block at the minimum and maximum locations you want to have visible to the player. I may find a better solution to this in the future, but that's the way it is for now
• Death "animation".
  • When the player dies, they will move back to the start position smoothly, rather than just teleporting back instantaneously. This was included in a previous update, which I didn't add a devlog for.
• Bugfixes.