New release for Linux

There is now a regular binary release for Linux rather than a Flatpak installer. If you already have the Flatpak version and want to continue using it then you can, and it will have access to the same updates as everyone else. However, I will not update the Flatpak installer when it breaks as a result of changes outside of my control at some point in the future.

This change has been done for two main reasons:

• Eliminating an error that occurs in the Flatpak version after users update their graphics driver, requiring a reinstall of the game.

• To reduce maintenance and simplify the process of generating releases.

The decision to use Flatpak was originally driven by uncertainty about which systems an OpenJDK binary would run on. The new binary release uses Azul Zulu builds, which currently lists the officially supported operating systems as: RHEL 9.x, RHEL 8.x, RHEL 7.x, SLES 15, SLES 12, CentOS Stream, Ubuntu 22.04, Ubuntu 20.04, Ubuntu 18.04, Debian 11, Debian 10, Wind River 8.x, Alpine Linux 3.11 or later, and Amazon Linux 2023. In practice I have not found a contemporary distribution they do not run on, and I have verified that they run on systems at least as old as Ubuntu 13.04 (2013) and Fedora 11 (2012), which are the oldest I've tested the game on to begin with.