[linter] Review linter setup (#3783)

- [2b395b9f] Fix command to lint markdown in `CONTRIBUTING.md`
- [fed4c86c] Re-activate JSDoc ESLint plugin and fix linting issues (As
far as I remember, we deactivated it when we upgraded to ESLint 9
because it was not compatible with it. But its now.)
- [a3d2064b] Refactor ESLint config to use `defineConfig` and
`globalIgnores` ([these are like new
defaults](https://eslint.org/blog/2025/03/flat-config-extends-define-config-global-ignores/))
- [a3d2064b] Replace `eslint-plugin-import` with
`eslint-plugin-import-x`
(https://github.com/es-tooling/module-replacements/blob/main/docs/modules/eslint-plugin-import.md)
- [86a185b6] Switch Stylelint config to flat format and simplify
Stylelint scripts (like we already did for ESLint and prettier)
  - [f5a2c541] Fix some typos

modules/default/newsfeed/newsfeed.js

@@ -181,6 +181,7 @@ Module.register("newsfeed", {
 	 * Gets a feed property by name
 	 * @param {object} feed A feed object.
 	 * @param {string} property The name of the property.
+	 * @returns {*} The value of the specified property for the feed.
 	 */
 	getFeedProperty (feed, property) {
 		let res = this.config[property];