feat: allow TS to be used in challenges (#56159)

client/utils/__fixtures__/challenges.ts

@@ -1,6 +1,20 @@
 import { ChallengeFile } from "../../src/redux/prop-types";
 
 export const challengeFiles: ChallengeFile[] = [
+  {
+    id: '0',
+    contents: 'some ts',
+    error: null,
+    ext: 'ts',
+    head: '',
+    history: ['index.ts'],
+    fileKey: 'indexts',
+    name: 'index',
+    seed: 'some ts',
+    tail: '',
+    editableRegionBoundaries: [],
+    usesMultifileEditor: true,
+  },
   {
     id: '1',
     contents: 'some css',

client/utils/sort-challengefiles.js

@@ -9,6 +9,8 @@ exports.sortChallengeFiles = function sortChallengeFiles(challengeFiles) {
     if (b.history[0] === 'index.jsx') return 1;
     if (a.history[0] === 'script.js') return -1;
     if (b.history[0] === 'script.js') return 1;
+    if (a.history[0] === 'index.ts') return -1;
+    if (b.history[0] === 'index.ts') return 1;
     return 0;
   });
   return xs;

client/utils/sort-challengefiles.test.js

@@ -14,10 +14,16 @@ describe('sort-files', () => {
       expect(sorted.length).toEqual(expected.length);
     });
 
-    it('should sort the objects into html, css, jsx, js order', () => {
+    it('should sort the objects into html, css, jsx, js, ts order', () => {
       const sorted = sortChallengeFiles(challengeFiles);
       const sortedKeys = sorted.map(({ fileKey }) => fileKey);
-      const expected = ['indexhtml', 'stylescss', 'indexjsx', 'scriptjs'];
+      const expected = [
+        'indexhtml',
+        'stylescss',
+        'indexjsx',
+        'scriptjs',
+        'indexts'
+      ];
       expect(sortedKeys).toStrictEqual(expected);
     });
   });