contentstack / app-sdk-docs Goto Github PK

The problem is with @contentstack/app-sdk itself, but github.com/contentstack/app-sdk/ is 404 for me, so I'll create an issue here.
I hope, it's all right.

I'm trying to create a custom application as described here, here and here.
I downloaded an app boilerplate from this link and I'm following steps in the guides.

But the first call to the sdk - ContentstackAppSdk.init() results in this error:

Am I missing some set-up steps, maybe? Or is it an issue with the sdk?

Thanks in advance for your help.