chore(docs): Move loadable-components instructions

docs/docs/using-client-side-only-packages.md

@@ -7,7 +7,7 @@ On occasion, you may need to use a function or library that only works client-si
 You'll need to use one of the workarounds outlined below if your project fails to compile with `gatsby develop` or `gatsby build` with an error like:
 
 ```shell
-Reference error: Window is not Defined
+Reference error: window is not defined
 ```
 
 ## Workaround 1: Use a different library or approach
@@ -21,7 +21,7 @@ In the component where you need it, load the package via CDN using a [`<script /
 To embed your script, you can:
 
 - Include it in a custom component as needed using [`react-helmet`](https://github.com/nfl/react-helmet).
-- Add the script tag directly in your base HTML using Gatsby's [html.js](/docs/custom-html/)
+- Add the script tag directly by using Gatsby's [`setHeadComponents`](/docs/reference/config-files/gatsby-ssr/#onRenderBody) in the `onRenderBody` API in `gatsby-ssr`.
 
 You should then follow React's guidelines for [Integrating with DOM Manipulation Plugins](https://reactjs.org/docs/integrating-with-other-libraries.html#integrating-with-dom-manipulation-plugins), using the methods available in the [React Component Lifecycle](https://reactjs.org/docs/react-component.html#the-component-lifecycle) to interact with the library you're using.
 
@@ -50,16 +50,41 @@ class MyComponent extends Component {
 }
 ```
 
-## Workaround 3: Load client-side dependent components with loadable-components
+## Workaround 3: Use React.lazy and Suspense on client-side only
+
+React.lazy and Suspense are not ready for server-side rendering, but they can be used by checking that the code is executed only on the client. While this solution is inferior to `loadable-components`, that works both on server side and client, it still provides an alternative for dealing with client-side only packages, without an added dependency. Remember that the following code could break if executed without the `isSSR` guard.
+
+```jsx
+import React from "react"
+
+const ClientSideOnlyLazy = React.lazy(() =>
+  import("../components/ClientSideOnly")
+)
+const MyPage = () => {
+  const isSSR = typeof window === "undefined"
+
+  return (
+    <>
+      {!isSSR && (
+        <React.Suspense fallback={<div />}>
+          <ClientSideOnlyLazy />
+        </React.Suspense>
+      )}
+    </>
+  )
+}
+```
+
+## Workaround 4: Load client-side dependent components with loadable-components
 
 Install [loadable-components](https://github.com/smooth-code/loadable-components) and use it as a wrapper for a component that wants to use a client-side only package.
 
 ```shell
 npm install @loadable/component
-# or use yarn
-yarn add @loadable/component
 ```
 
+And in your component:
+
 ```jsx
 import React, { Component } from "react"
 import PropTypes from "prop-types"
@@ -80,33 +105,6 @@ const LoadableBuyButton = Loadable(() => import("./ShopifyBuyButton"))
 export default LoadableBuyButton
 ```
 
-## Workaround 4: Use React.lazy and Suspense on client-side only
-
-React.lazy and Suspense are still not ready for server-side rendering, but they can still be used by checking that the code is executed only on the client.
-While this solution is inferior to `loadable-components`, that works both on server side and client, it still provides an alternative for dealing with client-side only packages, without an added dependency.
-Remember that the following code could break if executed without the `isSSR` guard.
-
-```jsx
-import React from "react"
-
-const ClientSideOnlyLazy = React.lazy(() =>
-  import("../components/ClientSideOnly")
-)
-const MyPage = () => {
-  const isSSR = typeof window === "undefined"
-
-  return (
-    <>
-      {!isSSR && (
-        <React.Suspense fallback={<div />}>
-          <ClientSideOnlyLazy />
-        </React.Suspense>
-      )}
-    </>
-  )
-}
-```
-
 > **Note:** There are other potential workarounds than those listed here. If you've had success with another method, check out the [contributing docs](/contributing/docs-contributions/) and add yours!
 
 If all else fails, you may also want to check out the documentation on [Debugging HTML Builds](/docs/debugging-html-builds/).

packages/gatsby/src/utils/api-node-docs.ts

@@ -371,7 +371,7 @@ export const preprocessSource = true
 export const onCreateBabelConfig = true
 
 /**
- * Let plugins extend/mutate the site's webpack configuration.
+ * Let plugins extend/mutate the site's webpack configuration. This method can be used by any Gatsby site, app, or plugin, not just plugins.
  *
  * See also the documentation for [`setWebpackConfig`](/docs/actions/#setWebpackConfig).
  *