Resolve #3544982 "Create a generic section container component"

Closes #3544982

Testing steps

• checkout drupalorg project to the branch here: https://gitlab.com/drupal-infrastructure/sites/drupalorg/-/merge_requests/181
• then spin up bluecheese with the branch from the issue fork. (link above)
• Add a section container to a landing page.
• Add a test heading and some test description text.
  • Note that these are not required, and often, the headings and/or descriptions of the constituent components should suffice. As such there is currently no max-widths on these, so long title or descriptions won't break to a new line unless you do it in the content itself.
• Add an arbitrary component or two.
  • Test each of the three possible background choices. Note that this list of options can easily be expanded to accommodate future iterations.
• Verify that each looks good.