New installer (Blom plz release)

[joe27g]

It's pretty clear that the current installer is in need of replacement, particularly because of the lack of cross-platform support. So the purpose of this issue is to combine #49, #70, and #92 and just say we need something new.

To summarize, the issues that need to be addressed are:

• Proper cross-platform support
• Option to choose beta branch or a custom fork
• Better path-finding, including custom paths and allowing spaces in usernames
• If the user needs dependencies, prompt them instead of letting it throw an error
• Attempt to download and extract files before injecting to avoid broken Discord installations
• Add other checks to make sure that files exist and add some error handling in index.js or the file that points to injection.js (since the injection method will likely be changed as well)

[PixelHir]

I think there also should be a static install directory, for example in %localappdata% since Discord is also stored in there, and some people do not know where the installer installs ED by default. It would make everything much easier