added the text box in the middle. added some content and finish the light and dark mode

js/darkmode.js

@@ -0,0 +1,19 @@
+let darkmode = localStorage.getItem('dark')
+const switch_button = document.getElementById("theme_switch")
+
+const enableDarkmode = () => {
+    document.body.classList.add('dark')
+    localStorage.setItem('darkmode' , 'active')
+}
+
+const disableDarkmode = () => {
+    document.body.classList.remove('dark')
+    localStorage.setItem('darkmode', null)
+}
+
+if(darkmode === 'avtive') enableDarkmode()
+
+switch_button.addEventListener("click", () => {
+    darkmode = localStorage.getItem('darkmode')
+    darkmode !== "active" ? enableDarkmode() : disableDarkmode()
+})