Add dark theme

Signed-off-by: Emmy D'Anello <ynerant@emy.lu>

index.html

@@ -78,4 +78,6 @@
       </div>
 
 </body>
+
+<script src="theme.js"></script>
 </html>

theme.js

@@ -0,0 +1,27 @@
+/*!
+ * Color mode toggler for Bootstrap's docs (https://getbootstrap.com/)
+ * Copyright 2011-2022 The Bootstrap Authors
+ * Licensed under the Creative Commons Attribution 3.0 Unported License.
+ */
+
+(() => {
+  'use strict'
+
+  const getPreferredTheme = () => {
+    return window.matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light'
+  }
+
+  const setTheme = function (theme) {
+    if (theme === 'auto' && window.matchMedia('(prefers-color-scheme: dark)').matches) {
+      document.documentElement.setAttribute('data-bs-theme', 'dark')
+    } else {
+      document.documentElement.setAttribute('data-bs-theme', theme)
+    }
+  }
+
+  setTheme(getPreferredTheme())
+
+  window.matchMedia('(prefers-color-scheme: dark)').addEventListener('change', () => {
+    setTheme(getPreferredTheme())
+  })
+})()