Issue #32: Adding basic CI for publishing to crates.io based on tags

[stuartlynn]

Addresses #32 I added a crates.io key to the actions secret keys

Workflow to publish should be something like

• Use cargo-bump to bump the version number and to git tag the release

cargo bump minor — git-tag

• push release tag to git

git push — follow-tags

Haven't tested this yet but will do next week

[andrewphilipsmith]

blocked by #77