Add the codeowners file that allows us to restrict scoped maintainers to dir/file scope

What does this MR do?

Introduces a code-owners file based on https://gitlab.com/gitlab-org/gitlab/-/blob/master/.gitlab/CODEOWNERS but customized to this project.

This includes:

• a new group for project wide maintainers that is @gitlab-org/maintainers/helm-charts-gitlab
• An approval from that group, or delivery or leadership by default for any file
• An exclusion for updating issue and merge request templates (matching gitlab project)
• Required approvals for specifical docs linting configuration
• Required approvals for architecture docs changes
• Required approvals for the codeowners file
• Optional approvals for docs, chart dependencies, and ci that ensure our scoped maintainers can continue to approve and merge for their scoped areas.

Future groups should be created for:

• zoeckt chart dependency maintainers so the dependency maintainers section doesn't get out of hand
• Charts architecture as we have maintainers progress to that level
• A distribution wide group for CI/CD once we have multiple maintainers that fit that across our distribution projects.

Related issues

Part of gitlab-org/distribution/team-tasks#1253 (closed)

Checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion.

Required

• Merge Request Title and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com
• When ready for review, MR is labeled "~workflow::ready for review" per the Distribution MR workflow

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• Documentation created/updated
• Tests added
• Integration tests added to GitLab QA
• Equivalent MR/issue for omnibus-gitlab opened
• Validate potential values for new configuration settings. Formats such as integer 10, duration 10s, URI scheme://user:passwd@host:port may require quotation or other special handling when rendered in a template and written to a configuration file.