feat: i18n user interface (#40306)

Co-authored-by: Oliver Eyton-Williams <ojeytonwilliams@gmail.com>

client/src/templates/Challenges/redux/execute-challenge-saga.js

@@ -12,6 +12,7 @@ import {
 } from 'redux-saga/effects';
 import { channel } from 'redux-saga';
 import escape from 'lodash/escape';
+import i18next from 'i18next';
 
 import {
   challengeDataSelector,
@@ -67,7 +68,7 @@ export function* executeChallengeSaga() {
 
   try {
     yield put(initLogs());
-    yield put(initConsole('// running tests'));
+    yield put(initConsole(i18next.t('learn.running-tests')));
     // reset tests to initial state
     const tests = (yield select(challengeTestsSelector)).map(
       ({ text, testString }) => ({ text, testString })
@@ -94,8 +95,8 @@ export function* executeChallengeSaga() {
     const testResults = yield executeTests(testRunner, tests);
 
     yield put(updateTests(testResults));
-    yield put(updateConsole('// tests completed'));
-    yield put(logsToConsole('// console output'));
+    yield put(updateConsole(i18next.t('learn.tests-completed')));
+    yield put(logsToConsole(i18next.t('learn.console-output')));
   } catch (e) {
     yield put(updateConsole(e));
   } finally {
@@ -205,6 +206,7 @@ function* previewChallengeSaga({ flushLogs = true } = {}) {
     }
   } catch (err) {
     if (err === 'timeout') {
+      // TODO: translate the error
       // eslint-disable-next-line no-ex-assign
       err = `The code you have written is taking longer than the ${previewTimeout}ms our challenges allow. You may have created an infinite loop or need to write a more efficient algorithm`;
     }