It's 2023. It should work better in dark mode out-of-the-box, without requiring the user to manually search the Internet, download/edit/copy config files.
1. At least one colour theme for dark mode should be included by default, without requiring the user to visit https://www.geany.org/download/themes/
2. A colour scheme for dark mode for the output panels should be included by default, and either let the user select it in the Preferences or automatically use it in dark mode, not [telling users to write a CSS file for it](https://github.com/geany/geany/issues/2520).
