feat: add footer component

src/components/footer.tsx

@@ -0,0 +1,14 @@
+import { useDark } from '~/utils'
+
+const Footer = () => {
+  const [isDark, toggleDark] = useDark()
+
+  return <>
+    {/* Toggle dark mode. */}
+    <button className={isDark ? 'i-carbon-sun' : 'i-carbon-moon'} onClick={() => toggleDark()}></button>
+    {/* Github icon. */}
+    <button className="icon-btn i-carbon-github"></button>
+  </>
+}
+
+export default Footer