Add a sample Google Cloud Function script

[markmcd]

Description of the change

This illustrates how to use Cloud Functions with the PaLM API.

As the default service account is un-scoped, there is an extra step required to work with the API. This script can be dropped in to a GCF editor to get the service account authorised against the PaLM API.

Motivation

A couple of users have gotten stuck doing this, so I figured we should drop a reference in here. If we don't want it in this repo I can dump it in a gist.

Type of change

Choose one: Other

Checklist

• I have performed a self-review of my code.
• I have added detailed comments to my code where applicable.
• I have verified that my change does not break existing code.
• My PR is based on the latest changes of the main branch (if unsure, please run git pull --rebase upstream main).
• I am familiar with the Google Style Guide for the language I have coded in.
• I have read through the Contributing Guide and signed the Contributor License Agreement.