[Benchmark] add test case

test/Benchmark/app/benchmark/string/match.rb

@@ -0,0 +1,21 @@
+# -*- coding: utf-8 -*-
+def string_match(x)
+  x.report "=~ with ASCII" do
+    100000.times do
+      "hello world" =~ /lo/
+    end
+  end
+
+  x.report "=~ with UTF8" do
+    100000.times do
+      "あいうえお" =~ /うえ/
+    end
+  end
+
+  x.report "=~ with dynamic regexp" do
+    str = "lo"
+    50000.times do
+      "hello world" =~ /#{str}/
+    end
+  end
+end