Add manuscript skeleton

[seabbs]

This PR closes #1 by adding a draft manuscript and moving the analysis plan contents into it for further fleshing out. The manuscript format used here requires at least quarto 1.5.0 and would ideall be rendered in CI and served at a pages site.

[zsusswein]

Thanks for doing this. Let's flesh it out and later issues and PRs.

[seabbs]

pre-commit is passing locally so I think these are false positives that were cleaned up in #17 and so once that is merged and this PR is updated we should see passing checks.