Sites Dimmer - sharp brightness reduction

Sites Dimmer automatically dims light-themed sites.

New:
- You can override the brightness for each site separately.
- Color inversion function available if you really want to darken.

Key features:
- Automatically determines theme types and turns on only on sites that have not bothered to create a theme for the dark mode.
- When reducing the brightness does not modify the color, everything looks as designed by the site.
- You control the brightness dimming level.
- If necessary, you can enable or disable dimming for each individual site.
- The extension icon indicates whether the current site brightness is dimmed.