Hermes: Include sdks/hermes-engine.podspec in release

Summary:
This file was added in D35300595 (ada6c71) and it needs to be part of the `react-native` release.

Changelog: [Internal]

Reviewed By: fkgozali

Differential Revision: D35983108

fbshipit-source-id: 0a1c437b953e575c0229b0382743c72b6c91bd0b

package.json

@@ -54,6 +54,7 @@
     "scripts/react_native_pods.rb",
     "scripts/react-native-xcode.sh",
     "sdks/hermesc",
+    "sdks/hermes-engine.podspec",
     "template.config.js",
     "template",
     "third-party-podspecs"