Add testing/README.md (denoland/deno_std#75)

Original: 9552f28daf

testing/README.md

@@ -0,0 +1,31 @@
+# Testing 
+
+## Usage
+
+```ts
+import { test, assert, equal, assertEqual } from 'https://deno.land/x/testing/testing.ts';
+
+test({
+  name: 'testing example',
+  fn() {
+    assert(equal("world", "world"));
+    assert(!equal("hello", "world"));
+    assert(equal({ hello: "world" }, { hello: "world" }));
+    assert(!equal({ world: "hello" }, { hello: "world" }));
+    assertEqual("world", "world");
+    assertEqual({hello: "world"}, {hello: "world"});
+  },
+});
+```
+
+Short syntax (named function instead of object):
+```ts
+test(function example() {
+  assert(equal("world", "world"));
+  assert(!equal("hello", "world"));
+  assert(equal({ hello: "world" }, { hello: "world" }));
+  assert(!equal({ world: "hello" }, { hello: "world" }));
+  assertEqual("world", "world");
+  assertEqual({hello: "world"}, {hello: "world"});
+});
+```