Feat: Ensure markdown formatting (#34547)

<!-- Please follow this checklist and put an x in each of the boxes, like this: [x]. It will ensure that our team takes your pull request seriously. -->

- [x] I have read [freeCodeCamp's contribution guidelines](https://github.com/freeCodeCamp/freeCodeCamp/blob/master/CONTRIBUTING.md).
- [x] My pull request has a descriptive title (not a vague title like `Update index.md`)
- [x] My pull request targets the `master` branch of freeCodeCamp.

Closes #34535

tools/scripts/ci/md-testing-utils.js

@@ -0,0 +1,125 @@
+const path = require('path');
+const fs = require('fs');
+const matter = require('gray-matter');
+
+const pass = true;
+
+const guideRoot = path.resolve(__dirname, '../../../guide');
+const challengeRoot = path.resolve(__dirname, '../../../curriculum/challenges');
+exports.guideRoot = guideRoot;
+exports.challengeRoot = challengeRoot;
+
+const allowedLangDirNames = [
+  'arabic',
+  'chinese',
+  'english',
+  'portuguese',
+  'russian',
+  'spanish'
+];
+
+exports.checkGuideFile = function checkGuideFile(file) {
+  const { stat, depth, name, fullPath } = file;
+  if (depth === 1) {
+    if (stat.isFile()) {
+      throw new Error(`${name} is not valid in the ${guideRoot} directory`);
+    }
+    if (!allowedLangDirNames.includes(name)) {
+      throw new Error(`${name} should not be in the ${guideRoot} directory`);
+    }
+  }
+  if (stat.isDirectory()) {
+    return checkDirName(name, fullPath);
+  }
+  return checkGuideFileName(name, fullPath);
+};
+
+function checkDirName(dirName, fullPath) {
+  return new Promise((resolve, reject) => {
+    if (dirName.replace(/(\s|\_)/, '') !== dirName) {
+      return reject(
+        new Error(`
+    Invalid character found in '${dirName}', please use '-' for spaces
+
+      Found in:
+        ${fullPath}
+    `)
+      );
+    }
+    if (dirName.toLowerCase() !== dirName) {
+      return reject(
+        new Error(`
+Upper case characters found in ${dirName}, all folder names must be lower case
+
+  Found in :
+    ${fullPath}
+`)
+      );
+    }
+    return resolve(pass);
+  });
+}
+
+function checkGuideFileName(fileName, fullPath) {
+  return new Promise((resolve, reject) => {
+    if (fileName !== 'index.md') {
+      return reject(
+        new Error(
+          `${fileName} is not a valid file name, please use 'index.md'
+
+      Found in:
+        ${fullPath}
+    `
+        )
+      );
+    }
+    return resolve(pass);
+  });
+}
+
+exports.checkFrontmatter = function checkFrontmatter(
+  { fullPath, stat },
+  options = {
+    validator() {
+      return true;
+    }
+  }
+) {
+  if (!stat.isFile()) {
+    return Promise.resolve(pass);
+  }
+  return new Promise((resolve, reject) =>
+    fs.readFile(fullPath, 'utf8', (err, content) => {
+      if (err) {
+        return reject(new Error(err));
+      }
+      try {
+        const { data: frontmatter } = matter(content);
+        const { validator } = options;
+        if (!validator(frontmatter)) {
+          return reject(
+            new Error(
+              `The article at: ${fullPath} failed frontmatter validation.`
+            )
+          );
+        }
+        return resolve(pass);
+      } catch (e) {
+        console.log(`
+
+  The below occured in:
+
+  ${fullPath}
+
+  `);
+        throw e;
+      }
+    })
+  );
+};
+
+function extractLangFromFileName({ path: relativePath }) {
+  return relativePath.split(path.sep)[0];
+}
+
+exports.extractLangFromFileName = extractLangFromFileName;