Documentation: Update docs to include reference key

[DeanKamali]

Can you update documentation to include an example / use case?

{ time: '09:00', available: false, reference: null },
{ time: '09:30', available: false, reference: null },
{ time: '10:00', available: true, reference: null },
{ time: '10:30', available: true, reference: null },
{ time: '11:00', available: true, reference: null },

[quinnlangille]

Hey @DeanKamali, sorry for the late reply but this repo was pretty much unmaintained for a while. I can see what I can do about updating the documentation in the next few weeks!