Support for ESM config files (with "type": "module")

If a project's package.json has "type": "module", Karma fails to load the config file. I'm wondering if there would be interest in supporting ESM config files in addition to CJS (and the other currently supported flavors).

While this might not be complete or the desired solution, it looks like something like this could add ESM config support: https://github.com/tschaub/karma/commit/99f1a92ec85a1dd2efbcd0faf1ad653e4b29cf8e