Update dark mode toggle in footer

Signed-off-by: PixelRobots <22979170+PixelRobots@users.noreply.github.com>

docs/_includes/nav_footer_custom.html

@@ -0,0 +1,31 @@
+<button class="btn js-toggle-dark-mode">☾ dark</button>
+
+<script>
+    const btnToggle = document.querySelector('.js-toggle-dark-mode');
+
+    if (localStorage.getItem('theme') === 'dark') {
+        jtd.setTheme('dark');
+        btnToggle.textContent = '☼ light';
+    } else {
+        jtd.setTheme('light');
+        btnToggle.textContent = '☾ dark';
+    }
+</script>
+
+<script>
+    const toggleDarkMode = document.querySelector('.js-toggle-dark-mode');
+
+    jtd.addEvent(toggleDarkMode, 'click', function () {
+        if (jtd.getTheme() === 'dark') {
+            jtd.setTheme('light');
+            toggleDarkMode.textContent = '☾ dark';
+            localStorage.setItem('theme', 'light');
+        } else {
+            jtd.setTheme('dark');
+            toggleDarkMode.textContent = '☼ light';
+            localStorage.setItem('theme', 'dark');
+        }
+    });
+</script>
+
+</br>