Allow using .. (range operator) as a means to refer to the parent directory

[dennisdoomen]

This PR implements support for using the C# range operator .. to navigate to parent directories, providing a more intuitive and concise syntax for path traversal.

Problem

Previously, navigating to parent directories required chaining multiple .Parent property accesses, which can become verbose:

var path = ChainablePath.Current.Parent.Parent.Parent / "file.txt";

Solution

With this change, you can now use the range operator .. for a cleaner syntax:

var path = ChainablePath.Current / .. / .. / .. / "file.txt";

This works exactly like the .Parent property but provides a more natural and readable way to express directory traversal.

Implementation Details

• Added a new / operator overload that accepts a Range parameter
• The operator validates that only the .. range operator (equivalent to Range.All) is used
• Throws ArgumentException with a clear error message if any other range is provided (e.g., 1..3)
• Available only on .NET 6.0+ and .NET Standard 2.1+ where the Range type is supported
• Delegates to the existing Parent property to ensure consistent behavior

Examples

// Navigate up and then to a sibling directory
var testPath = projectPath / .. / "tests" / "UnitTests.cs";

// Equivalent to:
var testPath = projectPath.Parent / "tests" / "UnitTests.cs";

// Complex navigation
var docsPath = ChainablePath.Current / .. / .. / "docs" / "README.md";

// Equivalent to:
var docsPath = ChainablePath.Current.Parent.Parent / "docs" / "README.md";

Closes #83

[github-actions]

Test Results

116 tests  +6   116 ✅ +6   1s ⏱️ -1s
  3 suites ±0     0 💤 ±0 
  3 files   ±0     0 ❌ ±0 

Results for commit c1a5458. ± Comparison against base commit 7418cc8.

♻️ This comment has been updated with latest results.

[coveralls]

Pull Request Test Coverage Report for Build 18627674698

Details

• 9 of 9 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.1%) to 97.101%

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Totals
Change from base Build 18627324930:	0.1%
Covered Lines:	239
Relevant Lines:	247

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💛 - Coveralls