feat(blog): Support custom color scheme for readers

[huyvohcmc]

I think memos-pub theme is set to follow the OS settings. Could we have a config in the repo to custom the theme to be either light or dark?

[thien-do]

Thanks! I think there will be 2 of this:

1. The author can choose dark, light or auto, as a default, using a config file #18
2. The reader can also choose (like when you use a reader app)

We will keep track of (1) in #18 , so let's use this issue for (2)

[thien-do]

How: https://tailwindcss.com/docs/dark-mode#toggling-dark-mode-manually