simplify navigation

scripts/main.js

@@ -1,7 +1,7 @@
 const theme_switcher = document.getElementById("theme-switcher");
 const imgs = document.getElementsByTagName("img");
 const sections_button = document.getElementById("sections-button");
-const sections_menu = document.getElementById("sections-menu");
+const sections_menu = document.getElementsByTagName("nav")[0];
 const main = document.getElementsByTagName("main")[0];
 
 let theme = window.localStorage.getItem("theme");