feat(lint): require spec_url if standard_track is true (#28810)

Introduces a linter that requires `spec_url` if 
`standard_track` is true for new features.

Existing violations are tracked in an exceptions list,
and get removed automatically when resolved.

---------

Co-authored-by: Leo McArdle <leo@mozilla.com>

Author: caugner

eslint.config.js

@@ -57,7 +57,7 @@ export default [
 
     languageOptions: {
       globals: {
-        ...globals.jest,
+        ...globals.mocha,
         ...globals.node,
         Atomics: 'readonly',
         SharedArrayBuffer: 'readonly',

lint/common/standard-track-exceptions.js

@@ -0,0 +1,33 @@
+import { readFile, writeFile } from 'node:fs/promises';
+import { dirname, join } from 'node:path';
+import { fileURLToPath } from 'node:url';
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = dirname(__filename);
+
+export const exceptionListPath = join(
+  __dirname,
+  './standard-track-exceptions.txt',
+);
+
+/**
+ * @returns {Promise<string[]>}
+ */
+export const getStandardTrackExceptions = async () =>
+  (await readFile(exceptionListPath, 'utf-8'))
+    .split('\n')
+    .map((line) => line.trim())
+    .filter((line) => line.length > 0 && !line.startsWith('#'));
+
+/**
+ *
+ * @param {Iterable<string>} features
+ */
+export const setStandardTrackExceptions = async (features) => {
+  const lines = (await readFile(exceptionListPath, 'utf-8'))
+    .split('\n')
+    .map((line) => line.trim());
+  const headerLines = lines.filter((line) => line.startsWith('#'));
+  const result = [...headerLines, ...[...features].sort()].join('\n');
+  await writeFile(exceptionListPath, result + '\n', 'utf-8');
+};