README.release_notes

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Release notes:

Note that this release increases the minor version and contains a number of breaking changes:

- The pseudopotential repository shipped with DFTK is now deprecated and slated for removal in a future version of DFTK. Please rely on the [PseudoPotentialData](https://github.com/JuliaMolSim/PseudoPotentialData.jl/) package for selecting pseudopotentials. Concretely this means that `list_psp` will be removed and `load_psp` will only be working with full paths to pseduopotential data files or e.g. combinations of `PseudoPotentialData.PseudoFamily` objects and an element symbol.