[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

stylelint.config.mjs

@@ -0,0 +1,7 @@
+const config = {
+	extends: ["stylelint-config-standard", "stylelint-prettier/recommended"],
+	root: true,
+	rules: {}
+};
+
+export default config;