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/citation.ts

@@ -0,0 +1,76 @@
+import $ from 'jquery';
+import {getCurrentLocale} from '../utils.ts';
+
+const {pageData} = window.config;
+
+async function initInputCitationValue(citationCopyApa, citationCopyBibtex) {
+  const [{Cite, plugins}] = await Promise.all([
+    import(/* webpackChunkName: "citation-js-core" */'@citation-js/core'),
+    import(/* webpackChunkName: "citation-js-formats" */'@citation-js/plugin-software-formats'),
+    import(/* webpackChunkName: "citation-js-bibtex" */'@citation-js/plugin-bibtex'),
+    import(/* webpackChunkName: "citation-js-csl" */'@citation-js/plugin-csl'),
+  ]);
+  const {citationFileContent} = pageData;
+  const config = plugins.config.get('@bibtex');
+  config.constants.fieldTypes.doi = ['field', 'literal'];
+  config.constants.fieldTypes.version = ['field', 'literal'];
+  const citationFormatter = new Cite(citationFileContent);
+  const lang = getCurrentLocale() || 'en-US';
+  const apaOutput = citationFormatter.format('bibliography', {template: 'apa', lang});
+  const bibtexOutput = citationFormatter.format('bibtex', {lang});
+  citationCopyBibtex.setAttribute('data-text', bibtexOutput);
+  citationCopyApa.setAttribute('data-text', apaOutput);
+}
+
+export async function initCitationFileCopyContent() {
+  const defaultCitationFormat = 'apa'; // apa or bibtex
+
+  if (!pageData.citationFileContent) return;
+
+  const citationCopyApa = document.querySelector('#citation-copy-apa');
+  const citationCopyBibtex = document.querySelector('#citation-copy-bibtex');
+  const inputContent = document.querySelector('#citation-copy-content');
+
+  if ((!citationCopyApa && !citationCopyBibtex) || !inputContent) return;
+
+  const updateUi = () => {
+    const isBibtex = (localStorage.getItem('citation-copy-format') || defaultCitationFormat) === 'bibtex';
+    const copyContent = (isBibtex ? citationCopyBibtex : citationCopyApa).getAttribute('data-text');
+    inputContent.value = copyContent;
+    citationCopyBibtex.classList.toggle('primary', isBibtex);
+    citationCopyApa.classList.toggle('primary', !isBibtex);
+  };
+
+  document.querySelector('#cite-repo-button')?.addEventListener('click', async (e) => {
+    const dropdownBtn = e.target.closest('.ui.dropdown.button');
+    dropdownBtn.classList.add('is-loading');
+
+    try {
+      try {
+        await initInputCitationValue(citationCopyApa, citationCopyBibtex);
+      } catch (e) {
+        console.error(`initCitationFileCopyContent error: ${e}`, e);
+        return;
+      }
+      updateUi();
+
+      citationCopyApa.addEventListener('click', () => {
+        localStorage.setItem('citation-copy-format', 'apa');
+        updateUi();
+      });
+
+      citationCopyBibtex.addEventListener('click', () => {
+        localStorage.setItem('citation-copy-format', 'bibtex');
+        updateUi();
+      });
+
+      inputContent.addEventListener('click', () => {
+        inputContent.select();
+      });
+    } finally {
+      dropdownBtn.classList.remove('is-loading');
+    }
+
+    $('#cite-repo-modal').modal('show');
+  });
+}