v0.4.2

<!-- Release notes generated using configuration in .github/release.yml at v0.4.2 -->

What's Changed

• feat: add MaxMemoryMB to MachineGuest by @dangra in https://github.com/superfly/fly-go/pull/214

Full Changelog: https://github.com/superfly/fly-go/compare/v0.4.1...v0.4.2