Formatting text with the Google Slides API Go Client

This is a Go port of the Python example here:

Video: https://www.youtube.com/watch?v=_O2aUCJyCoQ

The Go client has some issues with implementing the API as documented here which this mitigates.

• https://github.com/googleapis/google-api-go-client/issues/433
• https://stackoverflow.com/questions/59152588/how-to-fork-and-modify-the-google-api-go-client-sdk-to-resolve-slides-api-range