Add modulus benchmark

tests/ImageSharp.Benchmarks/General/Modulus.cs

@@ -0,0 +1,19 @@
+namespace ImageSharp.Benchmarks.General
+{
+    using BenchmarkDotNet.Attributes;
+
+    public class Modulus
+    {
+        [Benchmark(Baseline = true, Description = "Standard Modulus using %")]
+        public int StandardModulus()
+        {
+            return 255 % 256;
+        }
+
+        [Benchmark(Description = "Bitwise Modulus using &")]
+        public int BitwiseModulus()
+        {
+            return 255 & 255;
+        }
+    }
+}