v0.3.0.0

Wow, that took even longer than the last update...

Anyways, lots of changes! First the new features:

- You can now export your level as a .png and load .png levels. It should make sharing them easier, as most sites allow pasting images and copying or downloading them. It's also fun to see how the level data ends up looking.
.png images are (losslessly) compressed by default, while .lvl files aren't (all the darkness in the images show that), so saving a level as an image currently takes up like 10x less space than as .lvl! Attempting to load images that aren't levels will potentially crash the editor, of course.
For even more convenient sharing, you can automatically copy the image of the level to your clipboard from the "Level" tab, and load a copied level by pressing "Load from Clipboard" from the top left. This means you don't even need to download other people's levels manually anymore, just copy and paste the image! (Itch doesn't seem to properly support uploading images by pasting them, so until they fix that you'll have to manually upload the .png file if you share anything on the levels thread).
The clipboard stuff required making a custom plugin and doesn't currently work on Linux. But, the linux build has 0 downloads anyway...
FYI, the current format just dumps the .lvl data into the image. There's a header at the start, then the data for the tiles' positions, then the keys' data, then the doors' and locks' data, then some black pixels to round off the square image. Whenever I change how level saving works, the look of the images will change.
- You can now select doors/keys, and drag them around.
- Added autorun (press E to toggle it).
- Added a "New Level" button.
- Made it so holding shift allows you to place or delete many doors/keys without having to click for each one.

There's a system where loaded levels will attempt to "fix" themselves of oddities. Things like the player spawn point being outside the map, etc. I started work on a system where these levels will warn you of those problems before loading them, and you can choose to load them as they are or apply the automatic fixes. This means you can still open weird "troll" levels, even with features that the editor currently disallows. Speaking of which, I added some more of those restrictions:
- Doors with an amount of 0 are no longer allowed. This was confusing some people and they didn't work anyways.
- Placing big doors partially outside the level boundaries is no longer allowed.
- Locks can no longer be bigger than the door they're in (they still can if their number is too big; that's a bug).

Some misc stuff:

- Optimized level loading/resetting even more. Loading a big level for the first time can still take over 1/5th of a second, but resetting it will be way faster. Loading a smaller level and then the big one again will also be faster than the initial big load.
- Changed keyboard input so it's based on the physical position of keys. Shouldn't change anything for standard english-adjacent qwerty keyboards, but should fix some issues on other layouts... it could also make the issues worse if some keybinds collide. I should really get around to adding a keybind menu.
- Goal now doesn't visually "regrow" when reset.
- Added the undo sound, and a sound for making savestates (with the U key).

- Added the player shadow.
- When clicking "Save As..." the level's name is now suggested as the filename by default.
- The behaviour of the transparent door and key previews was improved, now they don't get "stuck" when you hover over invalid positions.
- The "More..." button is gone... for now ... !
- The menu at the top will now display a scrollbar if the contents don't fit (this took way more effort than it should've).

Now, bug fixes:

- "Fixed" the weird bug some people were having where the editor froze and showed a gradient square thing. That bug was probably an engine bug that got patched up in a newer update.
- Colliding with a door should more reliably open it now.
- Fixed bug where doors wouldn't always immediately open.