Add support to specify GitHub handles in data to differentiate speakers

[marcoroth]

Right now if two speakers have the exact same name we have no way of handling them as individual speakers.

Example: I believe that these two speakers aren't the same person, but share the exact name:

https://www.rubyvideo.dev/speakers/katie-miller

Maybe we can have an annotation in the data files that would allow use to differentiate between the speakers, something like:

  speakers:
    - Katie Miller <github:phedinkus>
    - Katie Miller <github:anotherkatie>

or maybe:

  speakers:
    - name: Katie Miller
      github: phedinkus

    - name: Katie Miller
      github: anotherkatie

[marcoroth]

There are also two "Tom Stuart"'s

• https://www.tomstuart.co.uk
• https://tomstu.art

Ironically, both spoke at Ru3y Manor: https://www.rubyvideo.dev/events/ruby-manor-3/speakers

[ChaelCodes]

How difficult would it be to use slug instead of github handle? Slug has to be unique anyway, right?