[Enhancement] `darken-x` and `lighten-x` for theme colors

The classes darken-x and lighten-x for these colors are very helpful. I wish they also worked with primary, secondary, and such theme colors. Same with the text versions.

Since these are supposedly the two most important colors in the palette, it’d be great if we have finer control over their shades. Currently, it requires a lot of custom classes to achieve these, at least for people like me who aren’t very comfortable with editing the default stylus variables/values.

[KaelWD]

I accidentally started this so I might as well actually do it. It’s pretty simple to do now with the dynamic theme system.

[johnleider]

I absolutely agree.