Temp folder is deleted when minecraft is closed. If the Node.js process ends abruptly, the folder will not delete. As a dirty way to counter this, the directory we extract native files to is cleaned in the preloader. Maybe we'll come up with a more elegant solution in the future.
When a user attemps to launch, the configured Java executable will be validated. If it is invalid, we will look for a valid installation. If no valid installation is found, the user will be prompted with an option to install Java. An option to decline needs to be added. If they choose to install, it will download, extract, and update the executable in the config. The game will then be launched.
Also added progress tracking for asset validations, as they can potentially take a bit longer. Showing progress assures the user that the program isn't stuck or broken.
Mojang fallback cannot be implemented due to limitations of decompressing large lzma files in node.js. This can probably be worked around by packaging with some command line binary, but it honestly it not worth it.
