[FEAT]: Adding Copilot for Business support (#2826)

* initial tests and implementation of Copilot for Business client API

* updated billing settings documentation

* renames and refactors - clarity and simplified

* using context to ensure license clean up

* extra documentation and used ApiOptions instead of custom class

* implemented observable clients

* Fixing convention issues

* renaming for clarity

---------

Co-authored-by: Nick Floyd <139819+nickfloyd@users.noreply.github.com>

Octokit/GitHubClient.cs

@@ -121,6 +121,7 @@ namespace Octokit
             Meta = new MetaClient(apiConnection);
             Actions = new ActionsClient(apiConnection);
             Codespaces = new CodespacesClient(apiConnection);
+            Copilot = new CopilotClient(apiConnection);
         }
 
         /// <summary>
@@ -395,6 +396,11 @@ namespace Octokit
         public IActionsClient Actions { get; private set; }
 
         public ICodespacesClient Codespaces { get; private set; }
+        
+        /// <summary>
+        /// Access GitHub's Copilot for Business API
+        /// </summary>
+        public ICopilotClient Copilot { get; private set; }
 
         static Uri FixUpBaseUri(Uri uri)
         {