docs: sync READMEs and add stacked overrides guide

- Updated README.md with Method 1 (Pre-built bundle) for NPM users
- Added Method 4: Stacked Overrides to both README.md and README.adoc
- Improved clarity of installation methods for better developer experience

Author: AMDphreak

README.adoc

@@ -122,6 +122,21 @@ ui:
   supplemental_files: ./node_modules/antora-dark-theme/supplemental-ui
 ----
 
+=== Method 4: Stacked Overrides (Deep Customization)
+
+To override the dark theme's own overrides with your project-specific customizations, use an array for `supplemental_files`. Paths listed later take precedence.
+
+[source,yaml]
+----
+ui:
+  bundle:
+    url: https://gitlab.com/antora/antora-ui-default/-/jobs/artifacts/HEAD/raw/build/ui-bundle.zip?job=bundle-stable
+    snapshot: true
+  supplemental_files:
+    - ./node_modules/antora-dark-theme/supplemental-ui
+    - ./site/src
+----
+
 == Live Demo
 
 See the dark theme in action: {url-demo}[Live Demo]

README.md

@@ -23,7 +23,28 @@ yarn add -D antora-dark-theme
 bun add -d antora-dark-theme
 ```
 
-Then configure your playbook file(s) (typically `antora-playbook.yml`) to load the supplemental UI from `node_modules`:
+Then configure your playbook file(s) (typically `antora-playbook.yml`) to use the theme.
+
+### Method 1: Use pre-built bundle (Recommended)
+
+The easiest way to use this theme is to point your Antora playbook directly to the latest pre-built UI bundle. This includes the Antora Default UI plus all dark mode enhancements without requiring any local package installation.
+
+```yaml
+ui:
+  bundle:
+    url: https://github.com/antora-supplemental/antora-dark-theme/releases/latest/download/ui-bundle.zip
+    snapshot: true
+```
+
+### Method 2: Use as npm dependency
+
+Install the package:
+
+```bash
+pnpm add -D antora-dark-theme
+```
+
+Then reference the supplemental UI from `node_modules`:
 
 ```yaml
 ui:
@@ -33,6 +54,20 @@ ui:
   supplemental_files: ./node_modules/antora-dark-theme/supplemental-ui
 ```
 
+### Method 3: Stacked Overrides (Deep Customization)
+
+To override the dark theme's own overrides with your project-specific customizations, use an array for `supplemental_files`. Paths listed later take precedence.
+
+```yaml
+ui:
+  bundle:
+    url: https://gitlab.com/antora/antora-ui-default/-/jobs/artifacts/HEAD/raw/build/ui-bundle.zip?job=bundle-stable
+    snapshot: true
+  supplemental_files:
+    - ./node_modules/antora-dark-theme/supplemental-ui
+    - ./site/src
+```
+
 ## Features
 
 - Dark mode toggle button (sun/moon icons)