Investigate how ThreeStyleTab detects Firefox theme

[rugk]

https://addons.mozilla.org/firefox/addon/tree-style-tab/

-> the setting:

[rugk]

Possibly:
https://github.com/piroor/treestyletab/blob/7ac29aead690b1c175fa2e6bb142cfb0a5306228/webextensions/sidebar/sidebar.js#L302

[CarolRDiz]

Hi, I found this: https://github.com/mdn/webextensions-examples/blob/main/theme-integrated-sidebar/sidebar.js
I hope it is still useful