Refactor nuclear_reaction_energy
Refactor nuclear_reaction_energy

 - Update docstrings (though exceptions need more updating)
 - Improve handling of tuples and strings when using the reactants and
   products keyword only arguments
 - Made some parts of the code more readable (e.g., by defining
   intermediate variables, etc.)
 - Improved exception handling
 - Included more f-strings in error messages

StanczakDominik/PlasmaPy