chore: add hrynco common library solution

- add the standalone HrynCo.Common solution and projects
- include the shared common library source and tests
- add package metadata and a repo gitignore

HrynCo.Common/EnvironmentNames.cs

@@ -0,0 +1,20 @@
+namespace HrynCo.Common;
+
+using System.Diagnostics.CodeAnalysis;
+
+[ExcludeFromCodeCoverage]
+public static class EnvironmentNames
+{
+    public const string Development = "Development";
+    public const string DockerDev = "DockerDev";
+    public const string IntegrationTests = "IntegrationTests";
+    public const string Production = "Production";
+    public const string Staging = "Staging";
+
+    public static readonly string[] DevelopmentLike =
+    [
+        Development,
+        DockerDev,
+        IntegrationTests
+    ];
+}