v0.28.0

What's Changed

• feat: concurrently build test projects by @hal3e in #625
• docs: implication that returning vectors is a thing. by @segfault-magnet in #659
• fuel core 0.13 upgrade by @Voxelot in #657
• release: bump versions to 0.28.0 by @digorithm in #666

Full Changelog: v0.27.0...v0.28.0