add Json.md

docs/005.Json.md

@@ -0,0 +1,45 @@
+Json
+====
+
+The plugin provides easy work with json.
+Method `encode()` returns the instance of `Psr\Http\Message\ResponseInterface`
+with encoded data in body of the response:
+```
+use Es\ControllerPlugins\PluginsTrait;
+
+class ExampleController
+{
+    use PluginsTrait;
+
+    public function fooAction()
+    {
+        $data = [
+            'foo' => 'bar',
+            'bat' => 'baz',
+        ];
+        return $this->json()->encode($data);
+    }
+}
+```
+
+The `decode` method returns the decoded data. On error is thrown exception.
+```
+use Es\ControllerPlugins\PluginsTrait;
+use Psr\Http\Message\ServerRequestInterface as Request;
+
+class ExampleController
+{
+    use PluginsTrait;
+
+    public function barAction(Request $request)
+    {
+        $body = (string) $request->getBody();
+
+        /* if unable to decode the content of request, the exception will be 
+         * thrown. In this case, the system itself must handle the exception 
+         * standard manner.
+         */
+        $data = $this->json()->decode($body);
+    }
+}
+```