v0.4.0

Notable changes

• Devex uplift by @jnewland in #14
• Initial GCS support by @jnewland in #12
• GCS docs by @jnewland in #19
• Don't fail when attempting to unlock an unlocked lock by @jnewland in #41

Full Changelog: https://github.com/urcomputeringpal/label-mutex/commits/v0.4.0