[feat] Add Response caching

Octokit/GitHubClient.cs

@@ -1,4 +1,5 @@
 using System;
+using Octokit.Caching;
 using Octokit.Internal;
 
 namespace Octokit
@@ -163,6 +164,21 @@ namespace Octokit
             }
         }
 
+        /// <summary>
+        /// Convenience property for setting response cache.
+        /// </summary>
+        /// <remarks>
+        /// Setting this property will wrap existing <see cref="IHttpClient"/> in <see cref="CachingHttpClient"/>.
+        /// </remarks>
+        public IResponseCache ResponseCache
+        {
+            set
+            {
+                Ensure.ArgumentNotNull(value, nameof(value));
+                Connection.ResponseCache = value;
+            }
+        }
+
         /// <summary>
         /// The base address of the GitHub API. This defaults to https://api.github.com,
         /// but you can change it if needed (to talk to a GitHub:Enterprise server for instance).