Move google docs instruction file into git to be more permanent and easier to access

[JuliusJacobsohn]

Google docs tend to vanish over time. If someone finds this in a few years, after the project is long abandoned, you may have already cleaned up your docs. Or you accidentally move the file and the link will become invalid, making the project near-unusable. I recreated the instructions in an .md file right in the repo.

[NicholasDawson]

Thanks for doing this, I think this is a great addition for the longevity of this project.

[JuliusJacobsohn]

I just added another commit. Not sure if this works, I never had a merge request with requested changes. If it doesn't, you can also just accept the request and change the email directly.