Added
- Added `EquationOfState.ideal_gas()` to initialize an equation of state that only consists of an ideal gas contribution. [204](https://github.com/feos-org/feos/pull/204)
- Added `PureRecord`, `SegmentRecord`, `Identifier`, and `IdentifierOption` to `feos.ideal_gas`. [205](https://github.com/feos-org/feos/pull/205)
- Added implementation of the Joback ideal gas model that was previously part of `feos-core`. [204](https://github.com/feos-org/feos/pull/204)
- Added an implementation of the ideal gas heat capacity based on DIPPR equations. [204](https://github.com/feos-org/feos/pull/204)
- Added re-exports for the members of `feos-core` and `feos-dft` in the new modules `feos::core` and `feos::dft`. [212](https://github.com/feos-org/feos/pull/212)
Changed
- Split `feos.ideal_gas` into `feos.joback` and `feos.dippr`. [204](https://github.com/feos-org/feos/pull/204)