Môsi gets an update to 0.41

This is a huge update - almost everything's been rewritten!

• You can now have multiple tabs open on desktop
• Worlds, rooms, and sprites can be rectangular (not just square!)
• Sprites are now referenced by name, which simplifies importing/exporting a great deal
• Actions are now called Behaviors, and Branches are now called Conditionals
• Things are faster - less lag in the editor! (hopefully!)
• A bunch of bug fixes and quality of life improvements

Converting from your old mosi world files should work fine, but please let me know if you run into problems! (The new stuff is saved under a different local storage key, so you won't have lost anything.)

Many thanks to everyone who tried this version on github first!

Also, I started a wiki for documentation, though it's pretty barebones at the moment: https://github.com/sarahgould/mosi/wiki