Add Threads registration example to README.md
diff --git a/README.md b/README.md
index 73bc7b8..a713aa9 100644
--- a/README.md
+++ b/README.md
@@ -138,3 +138,4 @@
         // Teardown code here.
       }
     }
+    BENCHMARK(BM_MultiThreaded)->Threads(2);