Adds dblock as a maintainer

[dlvenable]

Description

Adding @dblock as a maintainer as voted upon by the current maintainers.

He has made a number of contributions including fixing a bug (#217) that affected sigV4 signing.

Additionally, he has been active in the issues, PR reviews, and recent releases.

Issues Resolved

N/A

Check List

• [ ] New functionality includes testing.
  • [ ] All tests pass
• [ ] New functionality has been documented.
  • [ ] New functionality has documentation added
• [ ] Commits are signed as per the DCO using --signoff

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license. For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[dblock]

Thank you! Glad I can be of help.