doc: add link to ABI guide

Provides a link from the N-API reference to the guide discussing ABI
stability in greater depth.

Author: Gabriel Schulhof

doc/api/n-api.md

@@ -11,8 +11,8 @@ the underlying JavaScript runtime (ex V8) and is maintained as part of
 Node.js itself. This API will be Application Binary Interface (ABI) stable
 across versions of Node.js. It is intended to insulate Addons from
 changes in the underlying JavaScript engine and allow modules
-compiled for one version to run on later versions of Node.js without
-recompilation.
+compiled for one major version to run on later major versions of Node.js without
+recompilation. The [ABI Stability][] guide provides a more in-depth explanation.
 
 Addons are built/packaged with the same approach/tools
 outlined in the section titled [C++ Addons](addons.html).
@@ -4596,6 +4596,7 @@ idempotent.
 
 This API may only be called from the main thread.
 
+[ABI Stability]: https://nodejs.org/en/docs/guides/abi-stability/
 [ECMAScript Language Specification]: https://tc39.github.io/ecma262/
 [Error Handling]: #n_api_error_handling
 [Native Abstractions for Node.js]: https://github.com/nodejs/nan