add externals/globals note

Author: filipesilva

public/docs/ts/latest/cookbook/third-party-lib.jade

@@ -449,3 +449,9 @@ code-example(language="json").
 
   A good rule of thumb is to have all `dependencies` specified with a tilde `~`(`~1.2.3`),
   while your `peerDependencies` have a range (`"@angular/core": ">=4.0.0 <5.0.0 || >=4.0.0-beta <5.0.0"`).
+
+  Any extra dependency or peer Dependency that you add to `package.json` should also be added
+  to the `globals` and `external` array in the `rollupBaseConfig` variable in `./build.js`.
+
+  This ensures your library doesn't package extra libraries inside of it and instead uses the ones
+  available in the consuming app.