Lint all Markdown files and enable CI MD lint

[ben-alkov]

Maintainers will complete the following section:

• [x] Commit messages are descriptive enough
• [x] "Signed-off-by:" line is present in each commit
• [n/a] Code coverage from testing does not decrease and new code is covered
• [n/a] JSON/YAML configuration changes are updated in the relevant schema
• [n/a] Pull request includes link to an osbs-docs PR for user documentation updates

[packit-as-a-service[bot]]

Congratulations! One of the builds has completed. :champagne:

You can install the built RPMs by following these steps:

• sudo yum install -y dnf-plugins-core on RHEL 8
• sudo dnf install -y dnf-plugins-core on Fedora
• dnf copr enable packit/containerbuildsystem-koji-containerbuild-181
• And now you can install the packages.

Please note that the RPMs should be used only in a testing environment.