refactor: migrate browser scripts to ts

static/ts/anime.ts

@@ -0,0 +1,28 @@
+((): void => {
+  const toggleDropdown = (): void => {
+    const dropdown = document.getElementById('watchlist-dropdown')
+    if (!dropdown) {
+      return
+    }
+
+    dropdown.classList.toggle('open')
+  }
+
+  ;(window as Window & { toggleDropdown?: () => void }).toggleDropdown = toggleDropdown
+
+  document.addEventListener('click', (event: MouseEvent): void => {
+    const dropdown = document.getElementById('watchlist-dropdown')
+    if (!dropdown) {
+      return
+    }
+
+    const target = event.target
+    if (!(target instanceof Node)) {
+      return
+    }
+
+    if (!dropdown.contains(target)) {
+      dropdown.classList.remove('open')
+    }
+  })
+})()