feat: add flag for unhandled promise rejections

Author: kumavis

lib/client.js

@@ -121,8 +121,10 @@ extend(Raven.prototype, {
     if (this.captureUnhandledRejections) {
       var self = this;
       global.process.on('unhandledRejection', function(reason, promise) {
-        var context = promise.domain && promise.domain.sentryContext;
-        self.captureException(reason, context || {}, function(sendErr, eventId) {
+        var context = (promise.domain && promise.domain.sentryContext) || {};
+        context.extra = context.extra || {};
+        context.extra.unhandledPromiseRejection = true;
+        self.captureException(reason, context, function(sendErr, eventId) {
           if (!sendErr) {
             var reasonMessage = (reason && reason.message) || reason;
             utils.consoleAlert(