Add CI workflow

[chipsenkbeil]

Already have one for vimwiki-server, so can copy that one, but there are a couple of additions I would like to make:

1. Leverage cargo-hack to support publishing entity and entity_macros that have a cyclic dependency (it just removes dev dependencies)
2. Leverage cargo update -Z minimal-version as described in Command to update Cargo.lock to minimal versions rust-lang/cargo#4100
3. Leverage cargo-semvar to detect and enforce major/minor revision requirements as described in https://doc.rust-lang.org/cargo/reference/semver.html

[chipsenkbeil]

Closing out as CI workflow created. Not using any of above, but those could be moved to a deployment workflow.