feat(module): smart safelisting (#268)

Co-authored-by: Sébastien Chopin <seb@nuxtjs.com>

docs/content/1.getting-started/2.installation.md

@@ -45,6 +45,7 @@ As this module installs [@nuxtjs/tailwindcss](https://tailwindcss.nuxtjs.org/) a
 | `prefix`                 | `u`                    | Define the prefix of the imported components.    |
 | `global`                 | `false`                | Expose components globally.                      |
 | `icons`                  | `['heroicons']`        | Icon collections to load.                        |
+| `safelistColors`         | `['primary']`          | Force safelisting of colors.                     |
 
 ## Edge
 

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

@@ -33,13 +33,43 @@ Likewise, you can't define a `primary` color in your `tailwind.config.ts` as it
 We'd advise you to use those colors in your components and pages, e.g. `text-primary-500 dark:text-primary-400`, `bg-gray-100 dark:bg-gray-900`, etc. so your app automatically adapts when changing your `app.config.ts`.
 ::
 
-Components that have a `color` prop like [Avatar](/elements/avatar#chip), [Badge](/elements/badge#style), [Button](/elements/button#style) and [Notification](/overlays/notification#timeout) will use the `primary` color by default but will handle all the colors defined in your `tailwind.config.ts` or the default Tailwind CSS colors.
+Components having a `color` prop like [Avatar](/elements/avatar#chip), [Badge](/elements/badge#style), [Button](/elements/button#style), [Input](/elements/input#style) (inherited in [Select](/forms/select) and [SelectMenu](/forms/select-menu)) and [Notification](/overlays/notification#timeout) will use the `primary` color by default but will handle all the colors defined in your `tailwind.config.ts` or the default Tailwind CSS colors.
+
+Variant classes of those components are defined with a syntax like `bg-{color}-500 dark:bg-{color}-400` so they can be used with any color. However, this means that Tailwind will not find those classes and therefore will not generate the corresponding CSS.
+
+The module uses the [Tailwind CSS safelist](https://tailwindcss.com/docs/content-configuration#safelisting-classes) feature to force the generation of all the classes for the `primary` color **only** as it is the default color for all the components.
+
+Then, the module will automatically detect when you use one of those components with a color and will safelist it for you. This means that if you use a `red` color for a Button component, the `red` color classes will be safelisted for the Button component only. This will allow to keep the CSS bundle size as small as possible.
+
+There is one case where you would want to force the safelisting of a color. For example, if you've set the default color of the Button component to `orange` in your `app.config.ts`.
+
+```ts [app.config.ts]
+export default defineAppConfig({
+  ui: {
+    button: {
+      default: {
+        color: 'orange'
+      }
+    }
+  }
+})
+```
+
+This will apply the orange color when using a default `<UButton />`. You'll need to safelist this color manually in your `nuxt.config.ts` ui options as we won't be able to detect it automatically. You can do so through the `safelistColors` option.
+
+```ts [nuxt.config.ts]
+export default defineNuxtConfig({
+  ui: {
+    safelistColors: ['orange']
+  }
+})
+```
 
 ## Dark mode
 
 All the components are styled with dark mode in mind.
 
-Thanks to [Tailwind CSS dark mode](https://tailwindcss.com/docs/dark-mode#toggling-dark-mode-manually) `class` strategy and the [@nuxtjs/color-mode](https://github.com/nuxt-modules/color-mode) module, you literally have nothing to do.
+Thanks to [Tailwind CSS dark mode](https://tailwindcss.com/docs/dark-mode#toggling-dark-mode-manually) class strategy and the [@nuxtjs/color-mode](https://github.com/nuxt-modules/color-mode) module, you literally have nothing to do.
 
 ## Components