Update nextjs docs (#2080)

docs/pages/tutorials/integrating-with-nextjs.md

@@ -12,16 +12,12 @@ This page explains how to integrate Shoelace with a NextJS app.
 This is a community-maintained document. Please [ask the community](/resources/community) if you have questions about this integration. You can also [suggest improvements](https://github.com/shoelace-style/shoelace/blob/next/docs/tutorials/integrating-with-nextjs.md) to make it better.
 :::
 
-## Requirements
-
-This integration has been tested with the following:
+## Instructions - Next 12.1.6
 
 - Node: 16.13.1
 - NextJS: 12.1.6
 - Shoelace: 2.0.0-beta.74
 
-## Instructions
-
 To get started using Shoelace with NextJS, the following packages must be installed.
 
 ```bash
@@ -105,7 +101,109 @@ function MyApp({ Component, pageProps, URL }) {
 }
 ```
 
-### Environmental Variable
+## Instructions - Next 14.2.4
+
+- Node: v20.11.1
+- NextJS: 14.2.4
+- Shoelace: 2.15.1
+
+To get started using Shoelace with NextJS, the following packages must be installed.
+
+```bash
+yarn add @shoelace-style/shoelace
+```
+
+### Importing the Default Theme
+
+The next step is to import Shoelace's default theme (stylesheet) in your `_app.js` file:
+
+```css
+import '@shoelace-style/shoelace/dist/themes/light.css';
+```
+
+### Defining Custom Elements
+
+After importing the theme, you'll need to import the JavaScript files for Shoelace. However, this is a bit tricky to do in NextJS thanks to the SSR environment not having any of the required browser APIs to define endpoints.
+
+We'll want to create a component that uses [React's `useLayoutEffect`](https://reactjs.org/docs/hooks-reference.html#uselayouteffect) to add in the custom components before the first render:
+
+```javascript
+function CustomEls({ URL }) {
+  // useRef to avoid re-renders
+  const customEls = useRef(false);
+
+  useLayoutEffect(() => {
+    if (customEls.current) {
+      return;
+    }
+
+    import('@shoelace-style/shoelace/dist/utilities/base-path').then(({ setBasePath }) => {
+      setBasePath(`${URL}/static/static`);
+
+      // This imports all components
+      import('@shoelace-style/shoelace/dist/react');
+      // If you're wanting to selectively import components, replace this line with your own definitions
+
+      // import("@shoelace-style/shoelace/dist/components/button/button");
+      customEls.current = true;
+    });
+  }, [URL, customEls]);
+
+  return null;
+}
+```
+
+:::tip
+If we use `useEffect` instead of `useLayoutEffect`, the initial render will occur with the expected `sl-` props applied, but the subsequent render (caused by the `useEffect`) will remove those props as the custom components initialize. We _must_ use `useLayoutEffect` to have expected behavior
+:::
+
+:::tip
+This will import all Shoelace components for convenience. To selectively import components, refer to the [Using webpack](/getting-started/installation#using-webpack) section of the docs.
+:::
+
+You may be wondering where the `URL` property is coming from. We'll address that in the next few sections.
+
+### Using Our New Component CustomEls In Code
+
+While we need to use `useLayoutEffect` for the initial render, NextJS will throw a warning at us for trying to use `useLayoutEffect` in SSR, which is disallowed. To fix this problem, we'll conditionally render the `CustomEls` component to only render in the browser
+
+```javascript
+function MyApp({ Component, pageProps, URL }) {
+  const isBrowser = typeof window !== 'undefined';
+  return (
+    <>
+      {isBrowser && <CustomEls URL={URL} />}
+      <Component {...pageProps} />
+    </>
+  );
+}
+```
+
+### Importing Shoelace Components
+
+After importing the customElement in your `_app.tsx` e.g., you now can import the components.
+
+We will need to mark the component as 'use client'
+
+```javascript
+'use client';
+import dynamic from 'next/dynamic';
+
+const SlButton = dynamic(() => import('@shoelace-style/shoelace/dist/react/button'), {
+  loading: () => <p>Loading...</p>,
+  ssr: false
+});
+
+export default function Sample() {
+  return <SlButton>Button</SlButton>;
+}
+```
+
+:::warning
+Don't forget to mark your component to 'use client'.
+:::
+
+## Environmental Variable
 
 However, to make `setBasePath()` work as-expected, we need to know where the file is hosted. To do this, we need to set [environmental variables](https://nextjs.org/docs/basic-features/environment-variables). Create a `.local.env` file and put the following inside:
 
@@ -129,7 +227,7 @@ MyApp.getInitialProps = async context => {
 You'll need to set this `BASE_URL` variable inside the build process of whatever local build or CI/CD you have. This will need to be an absolute URL, as a relative URL will cause shoelace to throw a warning
 :::
 
-### webpack Config
+## webpack Config
 
 Next we need to add Shoelace's assets to the final build output. To do this, modify `next.config.js` to look like this.