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/tribute.ts

@@ -0,0 +1,57 @@
+import {emojiKeys, emojiHTML, emojiString} from './emoji.ts';
+import {htmlEscape} from 'escape-goat';
+
+function makeCollections({mentions, emoji}) {
+  const collections = [];
+
+  if (emoji) {
+    collections.push({
+      trigger: ':',
+      requireLeadingSpace: true,
+      values: (query, cb) => {
+        const matches = [];
+        for (const name of emojiKeys) {
+          if (name.includes(query)) {
+            matches.push(name);
+            if (matches.length > 5) break;
+          }
+        }
+        cb(matches);
+      },
+      lookup: (item) => item,
+      selectTemplate: (item) => {
+        if (item === undefined) return null;
+        return emojiString(item.original);
+      },
+      menuItemTemplate: (item) => {
+        return `<div class="tribute-item">${emojiHTML(item.original)}<span>${htmlEscape(item.original)}</span></div>`;
+      },
+    });
+  }
+
+  if (mentions) {
+    collections.push({
+      values: window.config.mentionValues ?? [],
+      requireLeadingSpace: true,
+      menuItemTemplate: (item) => {
+        return `
+          <div class="tribute-item">
+            <img src="${htmlEscape(item.original.avatar)}" width="21" height="21"/>
+            <span class="name">${htmlEscape(item.original.name)}</span>
+            ${item.original.fullname && item.original.fullname !== '' ? `<span class="fullname">${htmlEscape(item.original.fullname)}</span>` : ''}
+          </div>
+        `;
+      },
+    });
+  }
+
+  return collections;
+}
+
+export async function attachTribute(element, {mentions, emoji} = {}) {
+  const {default: Tribute} = await import(/* webpackChunkName: "tribute" */'tributejs');
+  const collections = makeCollections({mentions, emoji});
+  const tribute = new Tribute({collection: collections, noMatchTemplate: ''});
+  tribute.attach(element);
+  return tribute;
+}