v0.3.0

<!-- Release notes generated using configuration in .github/release.yml at v0.3.0 -->

What's Changed

• Add FsSizeGB field to MachineRootfs by @dangra in https://github.com/superfly/fly-go/pull/207

Full Changelog: https://github.com/superfly/fly-go/compare/v0.2.3...v0.3.0