added a bunch of content and placeholders to gather content for courses

Adding in sections for courses we need to have and offer. Where I found information, I added links. For each section, we need a video (ideal) or slides teaching the audience what it is, why they should care, how it can help them, how to use it/set up/integrate it and if there is a competing offer, how we differ.

For integration, we should call out who we integrate with (Jira, Jenkins, etc.), Why to integrate with GitLab, a Video and or screenshots on What the integration looks like in GitLab and how to use the integration in GitLab, How to integrate and what we offer as an Alternative to integration - cross promotion of our own tools.

For migration, we should talk about how to migrate from other VCS. Videos showing them the difference using GitLab versus their VCS, how to do it.