[gjs: 17/25] engine: Add missing headers

[Philip Chimento <pchimento src gnome org>]

commit 00f39892d9fea5ec3472438e2537a4ebefa81266
Author: Philip Chimento <philip chimento gmail com>
Date:   Mon May 20 18:50:32 2019 -0700

    engine: Add missing headers
    
    Some APIs in SpiderMonkey 68 have only moved to a separate header file
    and not otherwise changed.

 gjs/engine.cpp | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/gjs/engine.cpp b/gjs/engine.cpp
index 422d89b2..20ac1178 100644
--- a/gjs/engine.cpp
+++ b/gjs/engine.cpp
@@ -34,7 +34,9 @@
 #include <glib.h>
 
 #include "gjs/jsapi-wrapper.h"
+#include "js/ContextOptions.h"
 #include "js/Initialization.h"  // for JS_Init, JS_ShutDown
+#include "js/Promise.h"
 #include "js/Warnings.h"
 #include "js/experimental/SourceHook.h"
 #include "mozilla/UniquePtr.h"