docs: clarify remote config wording and add cross-link from Node SDK (#15342)

* docs: clarify remote config wording and add cross-link from Node SDK

Clarify Step 2 heading on the remote config page to make it clear the
secure API key is passed in options (not as the main constructor arg).

Add a callout in the Node SDK feature flags section pointing to the
remote config docs, so users who land on the Node SDK page can find
the correct setup instructions.

* Update contents/docs/libraries/node/index.mdx

Co-authored-by: Vincent (Wen Yu) Ge <29069505+gewenyu99@users.noreply.github.com>

---------

Co-authored-by: Vincent (Wen Yu) Ge <29069505+gewenyu99@users.noreply.github.com>

Author: 2 people

contents/docs/feature-flags/remote-config.mdx

@@ -20,7 +20,7 @@ import ObtainFeatureFlagsSecureAPIKey from "../integrate/_snippets/obtain-flags-
 
 <ObtainFeatureFlagsSecureAPIKey />
 
-## Step 2: Initialize PostHog with your feature flags secure API key
+## Step 2: Initialize PostHog with your feature flags secure API key in options
 
 import ConfigureFlagsSecureKey from "../integrate/_snippets/configure-flags-secure-key.mdx"
 

contents/docs/libraries/node/index.mdx

@@ -268,6 +268,8 @@ import NodeFeatureFlagsCode from '../../integrate/feature-flags-code/_snippets/f
 
 <NodeFeatureFlagsCode />
 
+> **Note:** For remote config flags, see the [remote config documentation](/docs/feature-flags/remote-config). Remote config requires the [Feature Flags secure API key](/docs/feature-flags/remote-config#step-1-find-your-feature-flags-secure-api-key) passed as the `personalApiKey` option.
+
 import LocalEvaluationIntro from "../../feature-flags/snippets/local-evaluation-intro.mdx"
 
 ### Local evaluation