docs: Add steps to custom theme instructions

README.md

@@ -32,7 +32,13 @@ In an effort to align with Filament's theming methodology you will need to use a
 @import 'tippy.js/dist/tippy.css';
 ```
 
-2. Add the plugin's views to your `tailwind.config.js` file.
+2. Add the tippy.js package to your dev dependencies.
+
+```sh
+npm install --save-dev tippy.js
+```
+
+3. Add the plugin's views to your `tailwind.config.js` file.
 
 ```js
 content: [
@@ -41,6 +47,24 @@ content: [
 ]
 ```
 
+4. Add the `tailwindcss/nesting` plugin to your `postcss.config.js` file.
+
+```js
+module.exports = {
+    plugins: {
+        'tailwindcss/nesting': {},
+        tailwindcss: {},
+        autoprefixer: {},
+    },
+}
+```
+
+5. Rebuild your custom theme.
+
+```sh
+npm run build
+```
+
 ## Upgrading from 2.x to 3.x
 
 1. Output is now set with an Enum, please update your files to use `TiptapOutput` in all place where you are setting the output, including the config file.