voting: automatic pull request merging based on votes

[cpritcha]

we could use a GitHub action that counts votes from qualified members. there are some existing options like

• https://github.com/marketplace/actions/git-democracy (allow members to have weighted votes and only have registered members vote)
• https://github.com/gitconsensus/GitConsensusCLI (allow registered members to vote)

[alee]

As a simpler first cut that doesn't require any work / configuration we could also simply count thumbs up and thumbs down emojis on a private repository with explicitly granted membership