feat: improve NuGet package metadata

[rodri-oliveira-dev]

Summary

Improves the NuGet package presentation and discoverability for TypedParameters.Dapper.SqlServer.

Changes

• improves the NuGet title and description
• expands package tags for Dapper, SQL Server, SqlClient, typed parameters, TVPs, and .NET discovery
• adds the package project URL
• adds a dedicated NuGet icon at resource/nuget-icon.png
• configures PackageIcon and packs the icon into the .nupkg
• preserves the existing package ID, assembly name, namespace, target frameworks, license, README, SourceLink, symbols, and package validation settings

Validation

• branch is based directly on the current main
• diff is limited to the package project file and the new icon
• icon is a 256x256 PNG suitable for NuGet package metadata