[Docu] documentation.

...emical_reactions/chemical_reaction/i_chemical_reaction.md

...eactions/chemical_reaction/t_first_order_rate_constant.md

...m/chemical_reactions/chemical_reaction/t_reaction_type.md

...ctions/chemical_reaction/t_stoichiometric_coefficients.md

...hemical_system/chemical_reactions/i_chemical_reactions.md

...ProjectFile/prj/chemical_system/t_number_of_components.md