Allow easy packaging of a single ROM

[tobiasvl]

It'd be awesome if it were easy to bundle a specific ROM with this emulator, set configuration defaults, and disable the menu.

For example, if I made a Game Boy game, I could package it with this emulator and upload it to itch.io, or host it on my own website or on GitHub Pages, to make it playable in the browser.

I envision this as a few new settings in manifest.webapp:

• Configuration defaults for all settings (nice to have anyway)
• Whether the menu should be displayed or not (if I set defaults, I don't necessarily want to confuse players with the menu)
• The file name of a ROM; if set, and the file exists, the emulator runs that ROM directly after boot

[sleepyparadox]

Yes please!

[redbrain]

Even better, turn it into a node module.
Expose a main function that takes a canvas, a ROM, and some basic options, and allow people to use it in their own projects.