Reduce allocations

[ghost1face]

• Minimize allocations and tighten performance

[Copilot]

Pull request overview

This PR focuses on reducing allocations in the Base62 conversion path and adding a BenchmarkDotNet harness to measure the impact of those changes within the solution.

Changes:

• Optimize Base62Converter by removing List<>/StringBuilder usage in hot paths (array-based base conversion and char-buffer string construction).
• Add a new Base62.Benchmark project (plus a helper script) to benchmark current code vs. the latest NuGet package version.
• Update solution configuration/platform entries and ignore BenchmarkDotNet artifacts.

Reviewed changes

Copilot reviewed 10 out of 11 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
benchmark.sh	Adds a simple script to run the benchmark project in Release.
Base62/Base62Converter.cs	Reworks encoding/decoding and base conversion to reduce allocations and improve performance.
Base62.sln	Adds the benchmark project and x86/x64 configurations.
Base62.Benchmark/Program.cs	Runs benchmarks and fetches latest NuGet package versions via dotnet package search.
Base62.Benchmark/BenchmarkConfig.cs	Defines BenchmarkDotNet jobs for current project + selected NuGet versions.
Base62.Benchmark/Base62Benchmark.cs	Adds benchmark cases for string/byte encode/decode scenarios (incl. leading zeros).
Base62.Benchmark/Base62.Benchmark.csproj	New benchmark project targeting net10.0, with conditional project vs. package reference.
Base62.Benchmark/Nuget/NugetPackage.cs	DTO for NuGet search JSON payload.
Base62.Benchmark/Nuget/NugetSourceResult.cs	DTO for NuGet search JSON payload.
Base62.Benchmark/Nuget/NugetSearchResultRoot.cs	DTO root for NuGet search JSON payload.
.gitignore	Ignores BenchmarkDotNet.Artifacts/.

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