Inform dark-reader that the website already supports dark theme builtin

[avestura]

Hello

Do you guys think if it's a good idea to somehow inform darkreader that the website is already on a dark theme or at least supports dark theme built-in?
This can be done using a meta tag:

<meta name="darkreader" content="supports-dark,is-dark" />

Darkreader might refuse to modify the theme of the page with respect to user configuration. User might want to:

1. Prevent modification: Respect the website's wish by stopping the darkreader from changing the theme of the page and show it in the dark theme version provided by the site itself
2. Override theme: Ignore the meta tag and always apply darkreader modifications

[Gusted]

We're tracking this issue over at #1536