White-on-black support

[peter-lyons-kehl]

Please support white text on black background (or light-on-dark).

• The content can come so from the website. Or
• the website may apply user preference for light-on-dark, or
• another extension may transform the content so. I use https://addons.mozilla.org/en-US/firefox/addon/dark-background-light-text.

(Side note: For GMail only I use https://addons.mozilla.org/en-US/firefox/addon/night-eye-dark-mode, and for Google Docs I use "DocsAfterDark" - but those two websites don't need/are not suitable for Reading Ruler. https://addons.mozilla.org/en-US/firefox/addon/dark-background-light-text is the most mainstream extension for light-on-dark, so could you support it, please. Ideally with its three modes.)