Update project linting tools and configuration

Add markdownlint-cli2 as asdf dependency, so both linters are available to asdf users.

Also, now that we have a Docker image (https://gitlab.com/gitlab-org/gitlab-docs/-/jobs/7981643564) with the latest markdownlint-cli2 in it (https://github.com/DavidAnson/markdownlint-cli2/compare/v0.13.0...v0.14.0), let's use it!

Let's also update our linter configuration from gitlab project.

Job that uses the new Docker image: https://gitlab.com/gitlab-org/gitaly/-/jobs/7991749654.