Return a PromiseCapability from "react"

Fixes #1443.

Author: ADKaster

index.bs

@@ -8325,8 +8325,9 @@ IDL [=promise type=] values are represented by JavaScript [=PromiseCapability=]
 
         Note: Not all callers will use the returned {{Promise}}. Implementations might wish to
         avoid creating |newCapability| in those cases.
-    1.  Return [$PerformPromiseThen$](|promise|.\[[Promise]], |onFulfilled|, |onRejected|,
+    1.  Perform [$PerformPromiseThen$](|promise|.\[[Promise]], |onFulfilled|, |onRejected|,
         |newCapability|).
+    1.  Return |newCapability|.
 
     Note: This algorithm will behave in a very similar way to the
     {{%Promise.prototype.then%|promise.then()}} method.