Add a github action sample workflow file for auto-publishing crates on
creation of 'v*' tags. The sample workflow assumes a non-workspace
setup, so that cargo publish can be run from the repository root (=
crate root).
For multi-crate repositories, repository_setup.sh will generate
derivatives of this file.
There is a useless `cd .` in the `run` step which only exists so that
sed can easily replace it with the path for crates in a workspace when
auto-generating workflows.
Signed-off-by: Patrick Roy <roypat@amazon.co.uk>
