Make interface in README equal to real interface

Author: kelunik

README.md

@@ -49,10 +49,17 @@ namespace Interop\Async;
  */
 interface Promise
 {
-    /**
+	/**
      * Registers a callback to be invoked when the promise is resolved.
      *
-     * @param callable(\Throwable|\Exception|null $exception, mixed $result) $onResolved
+     * The callback receives `null` as first parameter and `$value` as second parameter on success. It receives the
+     * failure reason as first parameter and `null` as second parameter on failure.
+     *
+     * If the promise is already resolved, the callback MUST be executed immediately.
+     *
+     * Warning: If you use type declarations for `$value`, be sure to make them accept `null` in case of failures.
+     *
+     * @param callable(\Throwable|\Exception|null $exception, mixed $value) $onResolved Callback to be executed.
      *
      * @return void
      */

src/Promise.php

@@ -3,7 +3,7 @@
 namespace Interop\Async;
 
 /**
- * Promise object representing the future value of an asynchronous operation.
+ * Representation of a the future value of an asynchronous operation.
  */
 interface Promise
 {