Add renovate config for repository.

[michaelwclark]

Description

Fixes #22

• [x] I have read the Adding Renovate to Existing Projects guide.
• [x] I have assigned this issue to myself avoid duplicating efforts with other potential contributors.
• [x] I have verified this repository does not already have Renovate configured (or proposed in an open PR by another contributor).
  • [x] If the renovate[bot] account has already auto-filed a Configure Renovate PR in this repository, I confirm that I will create a separate PR under my own GitHub account, using the initial PR as inspiration.
• [x] I confirm that I have added Renovate linting to this project's existing CI pipeline, or have created a new linting workflow if one doesn't already exist.
• [x] If this repository is currently configured to use GitHub's Dependabot, my PR will also deprecate support for Dependabot in order to avoid conflicts with Renovate.

Type of Change

• [ ] Bug Fix
• [ ] New Feature
• [ ] Breaking Change
• [ ] Refactor
• [ ] Documentation
• [x] Other (Ops configuration)