add theme switcher

src/pages/_document.js

@@ -5,11 +5,7 @@ export default function Document() {
     <Html>
       <Head>
         <link rel="preconnect" href="https://fonts.googleapis.com" />
-        <link
-          rel="preconnect"
-          href="https://fonts.gstatic.com"
-          crossOrigin="true"
-        />
+        <link rel="preconnect" href="https://fonts.gstatic.com" crossOrigin="true" />
         <link
           href="https://fonts.googleapis.com/css2?family=Poppins:ital,wght@0,300;0,400;0,500;0,600;1,300;1,400;1,500&display=swap"
           rel="stylesheet"