Create Graphics library. (#316)

* Fix BoundingRect unit tests.

* Create `graphics` library.

Source/MonoGame.Extended.Graphics/Batching/BatchCommandQueueOverflowException.cs

@@ -0,0 +1,20 @@
+using System;
+
+namespace MonoGame.Extended.Graphics.Batching
+{
+    /// <summary>
+    ///     The exception that is thrown when enqueuing draw commands into a
+    ///     <see cref="Batch{TVertexType,TBatchDrawCommandData}" />
+    ///     results in an overflow.
+    /// </summary>
+    /// <seealso cref="Exception" />
+    public class BatchCommandQueueOverflowException : Exception
+    {
+        internal BatchCommandQueueOverflowException(int maximumCommandsCount)
+            : base(
+                $"The maximum number of batch commands ({maximumCommandsCount}) has been reached. Consider increasing the maximum, reducing the number of commands, or flushing the commands to the GraphicsDevice."
+            )
+        {
+        }
+    }
+}