even more bugfixes

ofcourse critical bugs pop up when im trying to release.

the system tray icon wouldnt show up when running the single-file executable on any platform. that is now fixed.
plus a couple more things have been done to make Squirrel behave like a good cross platform app, like storing the data in the OS’s appdata directory.

there are some more things i would like to do but i think the app is in a releasable state and i’ve wanted to ship it for a while. I’ve set up the GitHub release and all the relevant instructions in the README. might be last devlog before ship #1.