Changed

• Upgrade Therion to 6.3.0
• Based on Ubuntu 24.04 LTS
• Compiled with cmake

Changes

• Installed texlive-lang-czechslovak and texlive-lang-cyrillic packages [#2]
• Use apt-get instead of apt when building [#2]

Version tag note:
Because therion version is not changed, in this release the -slavic suffix has been added.
In next release that suffix won't be used.