refactor: organise TypeScript config and migrate helpers (#44747)

* feat: allow more 1000 steps to be created at once

* refactor: start migrating to typescript

* refactor: delete-step to ts

* refactor: migrated some helpers

* refactor: migrate create-empty-steps

* refactor: migrate create-step-between

* refactor: finish migrating to TS

* refactor: migrate tests

* fix: ensure mock.restore is done after each test

* fix: prevent double-tscing

* fix: repair the tests

* chore: use ts-node for scripts

We don't need the performance boost of incremental compilation and
ts-node is easier to work with

* refactor: consolidate tsconfigs

* refactor: replace gulp

* fix: use ts-node for build-curriculum

* fix: allow ts compilation of config

* feat: create and use create:config script

* fix: add /config to eslint projects

* fix: remove gulp script

tools/challenge-helper-scripts/helpers/get-last-step-file-content.ts

@@ -0,0 +1,41 @@
+import fs from 'fs';
+import path from 'path';
+import { getChallengeSeeds } from '../utils';
+import { getProjectPath } from './get-project-path';
+import { ChallengeSeed } from './get-step-template';
+
+// Looks up the last file found with format `step-###.md` in a directory and
+// returns associated information to it. At the same time validates that the
+// number of files match the names used to name these.
+function getLastStepFileContent(): {
+  challengeSeeds: Record<string, ChallengeSeed>;
+  nextStepNum: number;
+} {
+  const filesArr: string[] = [];
+  const projectPath = getProjectPath();
+
+  fs.readdirSync(projectPath).forEach(fileName => {
+    if (
+      path.extname(fileName).toLowerCase() === '.md' &&
+      !fileName.endsWith('final.md')
+    ) {
+      filesArr.push(fileName);
+    }
+  });
+
+  const fileName = filesArr[filesArr.length - 1];
+  // eslint-disable-next-line @typescript-eslint/no-unsafe-assignment, @typescript-eslint/no-unsafe-member-access, @typescript-eslint/no-unsafe-call
+  const lastStepFileString: string = fileName.split('.')[0].split('-')[1];
+  const lastStepFileNum = parseInt(lastStepFileString, 10);
+  if (filesArr.length !== lastStepFileNum) {
+    throw `Error: The last file step is ${lastStepFileNum} and there are ${filesArr.length} files.`;
+  }
+
+  return {
+    // eslint-disable-next-line @typescript-eslint/no-unsafe-assignment
+    challengeSeeds: getChallengeSeeds(projectPath + fileName),
+    nextStepNum: lastStepFileNum + 1
+  };
+}
+
+export { getLastStepFileContent };