Web and Linux version enhancements

Both the itch.io/html (https://chaslinux.itch.io/sumash) and the Linux versions of Sumash have several changes.

• The size of the display has doubled (1024 x 576 from 512 x 288). This makes everything easier to see. Eventually, I intended to implement scaling up to 1920 x 1080 (any larger would look terrible). For now, this is a start.
• The green Snap Droids used to be the slowest enemy. They're still slow... sometimes. And sometimes they're not slow. Be careful approaching Snap Droids, they're a bit more dangerous than they used to be.
• There was an echoing issue with audio when shooting multiple enemies within a short period of time. Audio is still a problem, but hopefully lessened.

These updates have not been applied to the Windows download yet, sorry. I rarely use Windows at home or work anymore, so updates for Windows users lag behind a bit. GameMaker for Linux unfortunately cannot compile for a Windows target, so I have to use a Windows machine to compile for Windows. Rest assured, I'll release a Windows version of these changes in a day or two.