Added

System.DateOnly and System.TimeOnly polyfills

Full arithmetic support (AddDays, AddYears, etc.)

Correct day-number–based behavior for parity with modern .NET

System.Index and System.Range polyfills

Includes all compiler-required members

Compatible with C# lowering rules (^, ..) even when syntax is not used

Enables modern slicing semantics on legacy runtimes

Unified slicing helpers under ModernBCL.Core.Slicing

Array slicing (T[])

IList<T> slicing

String slicing (via char[])

DateOnly / DateTime slicing scenarios

Designed for C# 7.3 (no language upgrade required)

SystemSample console applications

DateOnly / TimeOnly usage

Index / Range semantics

Practical slicing examples (date, string, list)

feat: release ModernBCL.Core.BLC v1.2.0 with multi-targeting and majo…

…r enhancements

- Added multi-targeting support: net48, net481, net8.0
- Introduced HashAccumulator64 (64-bit hashing)
- Added full comparer suite: ObjectHashComparer, EnumerableHashComparer, SequenceHashComparer
- Added full Guard API with fluent syntax (Null, NullOrEmpty, NullOrWhiteSpace, OutOfRange)
- Added fuzz tests for hashing and guard clauses
- Added BenchmarkDotNet project for hash and guard performance tests
- Improved HashCode polyfill for stronger non-commutative mixing
- Fixed deterministic null-handling in hashing
- Cleaned project structure, improved test organization
- Enhanced .csproj metadata for NuGet publishing (tags, URLs, SourceLink)
- Updated README.md and CHANGELOG.md for version 1.2.0

Correct the README.md dotnet add and install-package version

Add project files.