Enhance documentation to clarify that promise options are exclusive to React on Rails Pro with the Node renderer

Author: AbanoubGhadban

docs/javascript/render-functions.md

@@ -76,6 +76,8 @@ const MyComponent = (props, _railsContext) => {
 
 ### 4. Promises of Strings
 
+This and other promise options below are only available in React on Rails Pro with the Node renderer.
+
 ```jsx
 const MyComponent = async (props, _railsContext) => {
   const data = await fetchData();

node_package/src/serverRenderReactComponent.ts

@@ -62,7 +62,7 @@ function processPromise(
 ): RenderStateHtml {
   if (!renderingReturnsPromises) {
     console.error(
-      'Your render function returned a Promise, which is only supported by a node renderer, not ExecJS.',
+      'Your render function returned a Promise, which is only supported by the React on Rails Pro Node renderer, not ExecJS.',
     );
     // If the app is using server rendering with ExecJS, then the promise will not be awaited.
     // And when a promise is passed to JSON.stringify, it will be converted to '{}'.