Migrate to poetry dependency management

Changes to steam library have regularly broken this package about once a year since it did not specify version constraints.

This problem has now been solved by migration to poetry for dependency management with version constraints and a version lock file.

Thanks to @Nixellion for #1 which brought support for steam lib v1.4.3, the latest as of this writing.

More quick filters!

New quick filters:

• score80 and score90 for the pickiest among us
• single for single-player

Also the script no longer crashes when an item in a quick filter alias list is invalid. Now that item is skipped and a error message is displayed.

Support space-separated quick filters

Makes it much easier to add multiple quick filters at once.

Also fix minor bug in decoding party time ascii art.

Fix Unix-like OS support

Should now work on both Windows and Unix-like OS.

Pre Alpha - Now with Windows support!

This should fix bugs in Windows.

Pre-Alpha

Tested only on Ubuntu 18.04.

Should work on Windows and MacOS.

Please let me know if you get this working on those OS!