Implement button to toggle theme.

Author: JackTench

src/app/home.tsx

@@ -1,10 +1,10 @@
-import { Button } from "@/components/ui/button";
+import { AppThemeToggleButton } from "@/components/libresplit/AppThemeToggleButton";
 
 export default function Home() {
   return (
     <div>
       <h1>LibreSplit</h1>
-      <Button>Test</Button>
+      <AppThemeToggleButton />
     </div>
   );
 }

src/components/libresplit/AppThemeToggleButton.tsx

@@ -0,0 +1,36 @@
+import { Button } from "../ui/button";
+import {
+  DropdownMenu,
+  DropdownMenuContent,
+  DropdownMenuItem,
+  DropdownMenuTrigger,
+} from "../ui/dropdown-menu";
+import { Moon, Sun } from "lucide-react";
+import { useTheme } from "next-themes";
+
+export function AppThemeToggleButton() {
+  const { setTheme } = useTheme();
+
+  return (
+    <DropdownMenu>
+      <DropdownMenuTrigger asChild>
+        <Button variant="outline" size="icon">
+          <Sun className="h-[1.2rem] w-[1.2rem] scale-100 rotate-0 transition-all dark:scale-0 dark:-rotate-90" />
+          <Moon className="absolute h-[1.2rem] w-[1.2rem] scale-0 rotate-90 transition-all dark:scale-100 dark:rotate-0" />
+          <span className="sr-only">Toggle theme</span>
+        </Button>
+      </DropdownMenuTrigger>
+      <DropdownMenuContent align="end">
+        <DropdownMenuItem onClick={() => setTheme("light")}>
+          Light
+        </DropdownMenuItem>
+        <DropdownMenuItem onClick={() => setTheme("dark")}>
+          Dark
+        </DropdownMenuItem>
+        <DropdownMenuItem onClick={() => setTheme("system")}>
+          System
+        </DropdownMenuItem>
+      </DropdownMenuContent>
+    </DropdownMenu>
+  );
+}