[Layout and Design] Add dark theme

[Korb]

Judging by the README.md text and the screenshot, reader-project currently only supports the light color theme.
It would be nice for reader to automatically select the dark theme according to Windows system dark mode setting.

[rahuldshetty]

@Korb project supports more than light and dark theme. It uses daisyUI so thanks to its common theming, we have almost all of its theming style. There are some screenshots in the website: https://rahuldshetty.github.io/reader-project/

The auto-detection part might be something that needs to be looked into.

[Korb]

@rahuldshetty, then apparently this Issue should be reclassified as [Doc]—and the README.md should be supplemented with the

- ◑ Light and dark theme support

line, and/or the screenshot should be replaced with a combined one:

Click to see screenshot