style improvement

assets/js/theme.js

@@ -0,0 +1,16 @@
+const light = '🌝', dark = '🌚';
+const LIGHT = 'light', DARK = 'dark';
+const themeSwitcher = document.getElementById('theme-switcher');
+
+themeSwitcher.innerHTML = localStorage.theme === LIGHT ? light : dark;
+
+themeSwitcher.addEventListener('click', function () {
+  const currentTheme = localStorage.theme,
+    newTheme = currentTheme === LIGHT ? DARK : LIGHT,
+    { classList } = document.querySelector('html'),
+    text = newTheme === LIGHT ? light : dark;
+  classList.remove(currentTheme);
+  classList.add(newTheme);
+  localStorage.theme = newTheme;
+  themeSwitcher.innerHTML = text;
+});