feat: option to follow the system-wide light/dark mode (#71)

src/components/widget/NavMenuPanel.astro

@@ -9,7 +9,7 @@ interface Props {
 
 const links = Astro.props.links;
 ---
-<div id="nav-menu-panel" class:list={["float-panel closed absolute transition-all fixed right-4 px-2 py-2"]}>
+<div id="nav-menu-panel" class:list={["float-panel float-panel-closed absolute transition-all fixed right-4 px-2 py-2"]}>
     {links.map((link) => (
         <a href={link.url} class="group flex justify-between items-center py-2 pl-3 pr-1 rounded-lg gap-8
             hover:bg-[var(--btn-plain-bg-hover)] active:bg-[var(--btn-plain-bg-active)] transition