v0.3.0.1

Added a web build! Downloading the game is still recommended, as it's hard to share levels made in the web version and (currently) basically impossible to import others' levels unless you manage to find where your browser is storing them...
To share levels, you can screenshot the level image (in the Level tab) and perfectly crop it.

Other than that, some changes:

- Fixed a bug where negative doors would crash due to an infinite recursion bug.
- Undoing with no undos left now properly resets the position to the start of the level instead of crashing the game.
- Made it so the level image can be properly copied from a screenshot of the image shown in the Level tab (for platforms where copying to clipboard doesn't work, a way to share images is to manually screenshot it and then trim and copy it in some image software, for example paint.net).
- Platforms where copying images to clipboard isn't supported now won't show the relevant buttons.
- The "Level Image" preview should now always be shown up-to-date. If you find any case where pressing "Copy to Clipboard" (or "Force Refresh" in platforms where copying isn't supported) still makes the image change, please let me know.