docs(theming): improve colors customization with tailwind

docs/content/1.getting-started/3.theming.md

@@ -27,6 +27,35 @@ Try to change the `primary` and `gray` colors by clicking on the :u-icon{name="i
 
 As this module uses Tailwind CSS under the hood, you can use any of the [Tailwind CSS colors](https://tailwindcss.com/docs/customizing-colors#color-palette-reference) or your own custom colors. By default, the `primary` color is `green` and the `gray` color is `cool`.
 
+When [using custom colors](https://tailwindcss.com/docs/customizing-colors#using-custom-colors) or [adding additional colors](https://tailwindcss.com/docs/customizing-colors#adding-additional-colors) through the `extend` key in your `tailwind.config.ts`, you'll need to make sure to define all the shades from `50` to `950` as most of them are used in the components config defined in [`ui.config.ts`](https://github.com/nuxt/ui/blob/dev/src/runtime/ui.config.ts). You can [generate your colors](https://tailwindcss.com/docs/customizing-colors#generating-colors) using tools such as https://uicolors.app/ for example.
+
+```ts [tailwind.config.ts]
+import type { Config } from 'tailwindcss'
+import defaultTheme from 'tailwindcss/defaultTheme'
+
+export default <Partial<Config>>{
+  theme: {
+    extend: {
+      colors: {
+        green: {
+          50: '#EFFDF5',
+          100: '#D9FBE8',
+          200: '#B3F5D1',
+          300: '#75EDAE',
+          400: '#00DC82',
+          500: '#00C16A',
+          600: '#00A155',
+          700: '#007F45',
+          800: '#016538',
+          900: '#0A5331',
+          950: '#052e16'
+        }
+      }
+    }
+  }
+}
+```
+
 ### CSS Variables
 
 To provide dynamic colors that can be changed at runtime, this module uses CSS variables. As Tailwind CSS already has a `gray` color, the module automatically renames it to `cool` to avoid conflicts (`coolGray` was renamed to `gray` when Tailwind CSS v3.0 was released).