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/admin/config.ts

@@ -0,0 +1,24 @@
+import {showTemporaryTooltip} from '../../modules/tippy.ts';
+import {POST} from '../../modules/fetch.ts';
+
+const {appSubUrl} = window.config;
+
+export function initAdminConfigs() {
+  const elAdminConfig = document.querySelector('.page-content.admin.config');
+  if (!elAdminConfig) return;
+
+  for (const el of elAdminConfig.querySelectorAll('input[type="checkbox"][data-config-dyn-key]')) {
+    el.addEventListener('change', async () => {
+      try {
+        const resp = await POST(`${appSubUrl}/admin/config`, {
+          data: new URLSearchParams({key: el.getAttribute('data-config-dyn-key'), value: el.checked}),
+        });
+        const json = await resp.json();
+        if (json.errorMessage) throw new Error(json.errorMessage);
+      } catch (ex) {
+        showTemporaryTooltip(el, ex.toString());
+        el.checked = !el.checked;
+      }
+    });
+  }
+}