feat(doc): Add sub-theme section

Author: sylus

content/en/_index.en.html

@@ -69,8 +69,8 @@ <h1 class="text-center mb-5">Drupal WxT Latest News</h1>
       <div class="item">
         <div class="header">
           <div class="content">
-            <div class="day">December 30</div>
-            <div class="year">2021</div>
+            <div class="day">January 4</div>
+            <div class="year">2022</div>
           </div>
         </div>
         <div class="title">
@@ -82,7 +82,7 @@ <h3>Drupal WxT <a href="https://github.com/drupalwxt/wxt/releases/tag/4.2.0">v4.
       <div class="item">
         <div class="header">
           <div class="content">
-            <div class="day">December 30</div>
+            <div class="day">January 2</div>
             <div class="year">2021</div>
           </div>
         </div>

content/en/docs/development/theming/_index.en.md

@@ -0,0 +1,107 @@
+---
+title: "Theming"
+linkTitle: "Theming"
+weight: 15
+type: "landing"
+draft: false
+translated: false
+resources:
+  - src: "**.{png,jpg}"
+    title: "Image #:counter"
+    params:
+      byline: "Image: Drupal / CC-BY-CA"
+categories:
+- wxt
+tags:
+- theming
+---
+
+Largely when doing any theme related work with **[Drupal WxT][wxt]** this almost always should be done in a sub-theme.
+
+For more on creating sub-themes please consult the official documentation:
+
+- **[Creating sub-themes][sub-themes]**
+
+To assist with sub-theme creation **[WxT Bootstrap][wxt_bootstrap]** provides an example starterkit that should be of benefit.
+
+> **Note**: Sub-themes are just like any other theme except they inherit the parent theme's resources.
+
+## Sub Theme Configuration
+
+a) Replace every instance of `THEMENAME` with your chosen machine name often of the pattern `<prefix>_bootstrap`.
+
+b) Enable your new sub-theme preferably via **[drush][drush]**:
+
+```sh
+drush en `<prefix>_bootstrap`
+drush cc css-js
+```
+
+c) Point to your new sub theme for **[WxT Library][wxt_library]** to properly load assets under **Themes Visibility** on the `/admin/config/wxt/wxt_library` page.
+
+## Notes
+
+### Inheriting Block Templates
+
+If the theme you are extending has custom block templates these won't be immediately inherited because a sub-theme creates copies of all the blocks in the parent theme and renames them with the sub-theme's name as a prefix. Twig block templates are derived from the block's name, so this breaks the link between these templates and their block.
+
+To fix this problem it requires a hook in the sub-theme by adding the following code snippet to the `THEMENAME.theme` file:
+
+### Programmatic Logic
+
+The following provides an example of how you can configure your sub theme to be installed as the default on a module install:
+
+```php
+/**
+ * Implements hook_modules_installed().
+ */
+function MODULENAME_modules_installed($modules) {
+    if (in_array('wxt', $modules)) {
+      \Drupal::configFactory()
+        ->getEditable('system.theme')
+        ->set('default', 'THEMENAME')
+        ->set('admin', 'claro')
+        ->save(TRUE);
+    }
+  }
+}
+```
+
+The following provides an example of how you can configure `wxt_library` to use your sub theme by creating a `config/install/wxt_library.settings.yml` file with the following contents:
+
+```yaml
+url:
+  visibility: 0
+  pages:
+    - 'admin*'
+    - 'imagebrowser*'
+    - 'img_assist*'
+    - 'imce*'
+    - 'node/add/*'
+    - 'node/*/edit'
+    - 'print/*'
+    - 'printpdf/*'
+    - 'system/ajax'
+    - 'system/ajax/*'
+theme:
+  visibility: 1
+  themes:
+    THEMENAME: THEMENAME
+    wxt_bootstrap: wxt_bootstrap
+minimized:
+  options: 1
+files:
+  types:
+    css: css
+    js: js
+wxt:
+  theme: theme-gcweb
+```
+
+<!-- Links Referenced -->
+
+[drush]:         https://www.drush.org/latest/
+[sub-themes]:    https://www.drupal.org/docs/theming-drupal/creating-sub-themes
+[wxt]:           https://github.com/drupalwxt/wxt
+[wxt_bootstrap]: https://www.drupal.org/project/wxt_bootstrap
+[wxt_library]:   https://www.drupal.org/project/wxt_library