Allow users to opt-in to proxies (#888)

* Allow users to opt-in to proxies

* Allow opting in to proxies on the WebSocket

src/Discord.Net.Rest/Net/DefaultRestClient.cs

@@ -22,7 +22,7 @@ namespace Discord.Net.Rest
         private CancellationToken _cancelToken;
         private bool _isDisposed;
 
-        public DefaultRestClient(string baseUrl)
+        public DefaultRestClient(string baseUrl, bool useProxy = false)
         {
             _baseUrl = baseUrl;
 
@@ -30,7 +30,7 @@ namespace Discord.Net.Rest
             {
                 AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate,
                 UseCookies = false,
-                UseProxy = false
+                UseProxy = useProxy,
             });
             SetHeader("accept-encoding", "gzip, deflate");
 

src/Discord.Net.Rest/Net/DefaultRestClientProvider.cs

@@ -4,16 +4,21 @@ namespace Discord.Net.Rest
 {
     public static class DefaultRestClientProvider
     {
-        public static readonly RestClientProvider Instance = url => 
+        public static readonly RestClientProvider Instance = Create();
+
+        public static RestClientProvider Create(bool useProxy = false)
         {
-            try
+            return url =>
             {
-                return new DefaultRestClient(url);                    
-            }
-            catch (PlatformNotSupportedException ex)
-            {
-                throw new PlatformNotSupportedException("The default RestClientProvider is not supported on this platform.", ex);
-            }
-        };
+                try
+                {
+                    return new DefaultRestClient(url, useProxy);
+                }
+                catch (PlatformNotSupportedException ex)
+                {
+                    throw new PlatformNotSupportedException("The default RestClientProvider is not supported on this platform.", ex);
+                }
+            };
+        }
     }
 }