2.1.2

docs: improve README with enhanced observe/safe examples and usage guidance

• Expanded observe and safe section with friendly headers and explanatory context
• Added beginner-friendly code samples demonstrating use of .observe(_:) and .safe(...) on collections
• Clarified purpose and use cases of safe accessors for out-of-bounds protection
• Improved readability and developer onboarding through narrative structure

Full Changelog: 2.1.1...2.1.2