Version 6.0

• merge modules into on file
• drop compatibility mode
• add reactants module, thanks to @Sonja-K
• fix issue #42
• use LaTeX's new hook mechanism
• get rid of scrlfile dependency
• update to l3text
• rename \Torr -> \torr
• new iupac command \normal
• resolve issue #45
• adapt to siunitx v3.0, implement units that have been removed from siunitx
• add Danish translations
• new translations module, move all translation declarations there