Add support for named and lazy values

[rojtjo]

This PR adds support for named and lazy values.

use FeatureNinja\TestingMatrix\Matrix;
use FeatureNinja\TestingMatrix\Value;

Matrix::create([
    'version' => [
        Value::of('8.3', 8.3),
        Value::of('8.4', fn () => 8.3),
    ],
    'data' => [
        Value::lazy('large-file', fn () => file_get_contents('/some/path'),
    ],
])

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Files with missing lines	Coverage Δ	Complexity Δ
src/Matrix.php	100.00% <100.00%> (ø)	7.00 <0.00> (+1.00)
src/Value.php	100.00% <100.00%> (ø)	5.00 <5.00> (?)