Document Docker Hub accounts in managed assets

[arminru]

trafficstars

Our Docker Hub profile otel and user opentelemetrybot are missing in assets.md: https://hub.docker.com/r/otel/ https://hub.docker.com/u/opentelemetrybot

[SergeyKanzhelev]

cross reference: https://github.com/open-telemetry/community/issues/353

[trask]

@open-telemetry/collector-maintainers @open-telemetry/collector-contrib-maintainer do you own the Docker Hub accounts?

[codeboten]

pinging @tigrannajaryan and @bogdandrutu who I think set it up

[atoulme]

cross reference: https://github.com/open-telemetry/community/issues/1348

[codeboten]

The accounts initially mentioned in the issue are now document here: https://github.com/open-telemetry/community/blob/main/assets.md#docker-hub, can this issue be closed?