Add tooling for converting program data to website posts/speaker data

[escowles]

Right now there is an older set of scripts for doing this data conversion at https://phette23.github.io/fromSheetsToJekyll/, and I have been developing my own local, Ruby-based scripts to do this task.

It would be better if there was a standardized set of tooling as part of the website repo. This should not need any dependencies beyond what Jekyll needs, so hopefully it's not a big additional maintenance burden.