JSAPI users are used to things breaking. It's a guarantee you can bank
on: if you use a new version of SpiderMonkey, something will be broken.
That would be fine, except no one is in charge of updating the
documentation when things change. The best guide to embedding
SpiderMonkey is my example on github, and I only got it to work by
pestering Mozilla debs on IRC.
https://github.com/Chaircrusher/SpiderMonkeyES6Example
It's also obsolete mere weeks after putting it on github since the
latest & greatest SpiderMonkey ESR has moved on.
If Mozilla is committed to having third parties embed SpiderMonkey,
making documentations updates a priority would be a great first step.