Chemical species and chemical reaction rules

For the implementation of the oxycat use case (https://git.scc.kit.edu/virtmat-tools/virtmat-models-and-data-analyses/-/issues/6) it will be helpful to create a small thermochemistry language. Here a suggestion for grammar:

ChemTerm:
  (coefficient = NUMBER)*
  species = [Species:ID]
;

ChemReaction: // add rule to Parameter
  'Reaction'
  educts += ChemTerm['+'] ( '=' | '->' )
  products += ChemTerm['+']
  (
    ('enthalpy' enthalpy = NumericalScalarParameter)?
    ('entropy' entropy = NumericalScalarParameter)?
    ('free energy' free_energy = NumericalScalarParameter)?
  )#
;

ChemSpecies: // add rule to Statement
  'Species'
  name = ID (
    ('enthalpy' enthalpy = NumericalScalarParameter)?
    ('entropy' entropy = NumericalScalarParameter)?
    ('free energy' free_energy = NumericalScalarParameter)?
    ('structure' structure = VarReference)?
  )#
;