Configure secrets on GH and Heroku for buildtime data fetching

[zenlex]

To facilitate static site build, we will use Next's getStaticProps() method to fetch data from GitHub Repos, Meetup, and Google Sheets. This will require configuration of secrets on both GitHub and Heroku. The data fetch will get run on each build, so the repo secrets will facilitate PR testing, and the Heroku secrets will facilitate deployment fetches. If there are no changes to the site other than potential updates to the external datasets, we should be able to just redeploy to update data to latest.

[zenlex]

Need to decide on approach for local development - either dummy dataset with shared keys or a secret sharing solution on a need to know basis for people working on those components.

[zenlex]

We will just pass keys to devs on a need to know basis and rotate if issues are suspected.