Add PackagePair class

StabilityMatrix.Core/Models/PackagePair.cs

@@ -0,0 +1,9 @@
+using StabilityMatrix.Core.Models.Packages;
+
+namespace StabilityMatrix.Core.Models;
+
+
+/// <summary>
+/// Pair of InstalledPackage and BasePackage
+/// </summary>
+public record PackagePair(InstalledPackage InstalledPackage, BasePackage BasePackage);