Document Draft dependencies in a minimal Linux container

[radu-matei]

If you want to install Draft in an Alpine container, you need some basic dependencies, such as git or curl, which don't come by default with Alpine, as seen in #779 - document all the prerequisites for installing Draft in a minimal container.

[bacongobbler]

Just an FYI that the requirement on bash has likely been removed in #764 :)

[squillace]

This is a great thing to do. I'd love it.

[radu-matei]

@squillace - it just needs to be in a PR: https://github.com/Azure/draft/issues/779#issuecomment-391719114