Lightning Utilities 0.3.0

What's Changed

• Copy over the rank-zero utilities by @carmocca in #36
• Copy over is_overridden by @carmocca in #35
• Update version for a 0.3.0 release by @carmocca in #40
• Integrate StrEnum by @carmocca in #38
• Copy over get_all_subclasses by @carmocca in #39
• Update about.py description by @carmocca in #41

Full Changelog: v0.2.0...v0.3.0