CSS stylesheets not found

Hi,

I tried to add themed css files to my legacy plugin.

They are placed in src/css/{light,dark}.css

and loaded in module.ts like this:

import { loadPluginCss } from '@grafana/runtime';

loadPluginCss({
  dark: 'plugins/geeksrus-mqtt-panel/css/dark.css',
  light: 'plugins/geeksrus-mqtt-panel/css/light.css',
});

But this lead to the error in console:

Refused to apply style because its MIME type (‘text/html’) is not a supported stylesheet MIME type, and strict MIME checking is enabled.

When I try to load the link http://localhost:3000/public/plugins/geeksrus-mqtt-panel/css/light.css with a browser I get 404 which is likely the source of the mime issue.

What do I need to do to publish the css files?