Integrate with Porter's website

[carolynvs]

I am starting to put docs in docs/content that are intended to be hosted on porter's website. Let's figure out how to make that happen. Right now the site has a blurb about the operator at https://release-v1.porter.sh/operator.

• Move the index page for the operator into the operator's repo.
• Update Porter's magefile so that it adds the operator repo as a submodule and symlinks the content directory appropriately.
• Make sure that the site renders fine for mage docsPreview and uses a local copy of the operator when it's available, so that we can see how the site will look locally.
• Trigger a build of the v1 website when doc changes are merged to the operator reporsitory #147

[carolynvs]

Close this in favor of the remaining subtask issues that I have split out