v2.4.0

• New features
  • Add GGA functionals!
    • Add internal PBE, PBEsol, and Chachiyo functionals
    • Option to use all GGAs from Libxc using pylibxc or PySCF
• Miscellaneous
  • Add Thomas-Fermi and von Weizsäcker kinetic energy density functions
  • Rewrite functionals for better readability
  • Fix Torch operators in some edge cases
  • Merge configuration files in tox.ini
  • Update minimum versions of dependencies