Add a clear console function (#110)

CliFx/Infrastructure/FakeConsole.cs

@@ -85,6 +85,11 @@ namespace CliFx.Infrastructure
             }
         }
         
+        /// <inheritdoc />
+        public void Clear()
+        {
+        }
+
         /// <inheritdoc />
         public virtual void Dispose() => _cancellationTokenSource.Dispose();
     }

CliFx/Infrastructure/IConsole.cs

@@ -82,6 +82,11 @@ namespace CliFx.Infrastructure
         /// </para>
         /// </remarks>
         CancellationToken RegisterCancellationHandler();
+        
+        /// <summary>
+        /// Clears the console buffer and corresponding console window of display information.
+        /// </summary>
+        void Clear();
     }
 
     /// <summary>

CliFx/Infrastructure/SystemConsole.cs

@@ -90,6 +90,9 @@ namespace CliFx.Infrastructure
             return (_cancellationTokenSource = cts).Token;
         }
         
+        /// <inheritdoc />
+        public void Clear() => Console.Clear();
+
         /// <inheritdoc />
         public void Dispose()
         {