Convert frontend code to typescript (#31559)

None of the frontend js/ts files was touched besides these two commands
(edit: no longer true, I touched one file in
61105d0618
because of a deprecation that was not showing before the rename).

`tsc` currently reports 778 errors, so I have disabled it in CI as
planned.

Everything appears to work fine.

web_src/js/features/comp/SearchUserBox.ts

@@ -0,0 +1,51 @@
+import $ from 'jquery';
+import {htmlEscape} from 'escape-goat';
+
+const {appSubUrl} = window.config;
+const looksLikeEmailAddressCheck = /^\S+@\S+$/;
+
+export function initCompSearchUserBox() {
+  const searchUserBox = document.querySelector('#search-user-box');
+  if (!searchUserBox) return;
+
+  const $searchUserBox = $(searchUserBox);
+  const allowEmailInput = searchUserBox.getAttribute('data-allow-email') === 'true';
+  const allowEmailDescription = searchUserBox.getAttribute('data-allow-email-description') ?? undefined;
+  $searchUserBox.search({
+    minCharacters: 2,
+    apiSettings: {
+      url: `${appSubUrl}/user/search?active=1&q={query}`,
+      onResponse(response) {
+        const items = [];
+        const searchQuery = $searchUserBox.find('input').val();
+        const searchQueryUppercase = searchQuery.toUpperCase();
+        $.each(response.data, (_i, item) => {
+          const resultItem = {
+            title: item.login,
+            image: item.avatar_url,
+          };
+          if (item.full_name) {
+            resultItem.description = htmlEscape(item.full_name);
+          }
+          if (searchQueryUppercase === item.login.toUpperCase()) {
+            items.unshift(resultItem);
+          } else {
+            items.push(resultItem);
+          }
+        });
+
+        if (allowEmailInput && !items.length && looksLikeEmailAddressCheck.test(searchQuery)) {
+          const resultItem = {
+            title: searchQuery,
+            description: allowEmailDescription,
+          };
+          items.push(resultItem);
+        }
+
+        return {results: items};
+      },
+    },
+    searchFields: ['login', 'full_name'],
+    showNoResults: false,
+  });
+}