Add average power metrics, bump dependencies

What's Changed

• Bump github.com/prometheus/client_golang from 1.10.0 to 1.11.1 by @dependabot in #7
• Re-add average power consumption and update documentation by @jmesserli in #8

New Contributors

• @jmesserli made their first contribution in #8

Full Changelog: 2.0.1...2.1.0