fix(release-it): remove git tag check from release.sh

The git describe logic in release.sh to get the latest tag SHA is flawed in that it causes an error if the repo doesn't yet contain any tags. I think I've overcomplicated the script by including this check. Therefore, this merge request removes this unnecessary manual check and instead simply falls back to release-it's default behaviour, which is to use version 0.0.0 as a default if it can't detect a previous release.

Closes #84 (closed)