Add Dependabot config (#91)
Add Dependabot config (#91)

See:
https://docs.github.com/en/code-security/supply-chain-security/keeping-your-dependencies-updated-automatically/configuration-options-for-dependency-updates

GUS-W-9981100.
heroku/heroku-maven-plugin,heroku/heroku-maven-plugin,heroku/heroku-maven-plugin