Linux (and mac) support

[geefr]

Opening the PR early for feedback/discussion area

Disclaimer: I'm a C++ engineer by trade, will likely make javascript faux-pas

Linux status:

• Target added to package for Linux
• At the moment just packages as zip, could build .deb or .rpm packages for installation to system
• Tried to get AppImage support working, builder didn't seem to work
• When packaged as zip everyone.dance can be run, seems to work as expected
• But due to electron packaging switching to PIE format binaries needed to run from terminal - file manager doesn't recognise the everyone.dance binary on double-click
• UI launches, detects themes/can be installed
• Gameplay/score updates working, at least in stepmania-5.1, non-portable installation

Mac status:

• Target added to package for Mac, packaging as zip (I think an osx app package would be fine, but there's security/signing to worry about these days perhaps?)
• I assume it works - Things seem to work on Linux so far, so it should at least launch

My dev system is Linux Mint 20.x, I assume the linux/mac packages can be built on windows as well?

On a side note - Are releases currently being build by hand, and would you like github actions setup for the repo?

[benank]

Great stuff so far!

In terms of installation packages, I'm not sure how they work on Linux/Mac, but Windows needs it to be signed and that costs extra money, which is why it's just an executable right now.

I was able to make the Linux version on Windows but not the Mac version.

Releases are currently being built by hand, yep! I'd love to set up github actions to automate that.

[geefr]

Alright, if I didn't break anything in that last commit, and the changes aren't terrible style-wise for javascript I think that's good enough for the first Linux/Mac release. At least on my laptop I extracted the archive, ran it, installed, and got score updates out of sm.

Mainly just moved code around, but added in 'os' to be able to work out what platform it's running on. The SMInstallation class may be a bit unecesarrily stateful, but I couldn't work out how to just do a bunch of functions without wrapping them in a class, fell back to objectified/stateful approach.

[benank]

Thanks! Turns out that you did break things (as I think defaulting to StepMania 5 would be better than unknown - everyone loves to rename their install dirs, and the default doesn't include "5.0", but rather just "5").

The rest of it seems pretty solid. I'm going to merge it and fix the dir default case and will release a new build (for all platforms) soon.