Cookbook: CI releases a vendor contract

# GitHub Actions sketch
- run: npm i -g @doctransit/cli
- run: |
    doctransit docs create \
      --template "$TEMPLATE_ID" \
      --signer "Vendor <$VENDOR_EMAIL>" \
      --name "Vendor MSA $GITHUB_SHA" \
      --send
  env:
    DOCTRANSIT_API_KEY: ${{ secrets.DOCTRANSIT_API_KEY }}