Discourse comments follow up

The Discourse integration works well. You can see the topics being created under https://forum.gitlab.com/c/docs-comments, but for the time being this is a hidden category, meaning only forum moderators/admins can see it. That's done because:

• Every single page of docs is being processed and added as a topic at the moment. We don't need them all, so we'll have to be selective.
• Currently, that's almost 500 topics created, that otherwise would be flooding the forum's landing page.

What needs to be done in GitLab:

• Mark which files we don't need to have comments https://gitlab.com/gitlab-org/gitlab-ce/issues/39677
• Every document needs to have an H1 heading, otherwise the topic in Discourse is created with GitLab Documentation title and that's confusing https://gitlab.com/gitlab-org/gitlab-ce/issues/39678
• Every document needs to have a proper, descriptive title (H1). Bad example https://docs.gitlab.com/ee/ci/services/redis.html which will create a Using Redis topic in Discourse. That's not very helpful, using Redis where/how? https://gitlab.com/gitlab-org/gitlab-ce/issues/39679

In Discourse:

• Start fresh by making a new category (hidden at the beginning) that will ultimately serve as the docs site official category where topics will be created.

Questions:

• Are redirects created as well? I need to check. => They shouldn't be as they are not using the template where comments are defined.

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PS: Reminder how this integration works https://meta.discourse.org/t/embedding-discourse-comments-via-javascript/31963