make all UserAgent checks case-insensitive (bugfix)

Available on GitHub Packages: docker pull ghcr.io/cogolabs/beyond:v1.8.8

What's Changed

• Handle alternate spelling for docker user-agent by @leonardochen in #4

New Contributors

• @leonardochen made their first contribution in #4

Full Changelog: v1.8.7...v1.8.8