feat: add dark and light theme flavors

[egel]

Add dark and light theme flavors?

• hard
• medium
• soft

[egel]

After writing this issue, I am still wondering if these flavors make sense in the tmux theme...

The reasoning that remains in my mind is as follows. Suppose we look at an editor, for example, someone who is using Vim with also a gruvbox theme with "hard" flavor. Then the Vim editor has indeed different backgrounds (that are defined by flavors), and also many more elements that require different colors. Although the color of the bottom action bar remains the same.

In our case (in tmux), we have one small bar, which in the case of the schematic picture above, should remain with the same color. Maintaining this momentum, the tmux theme also remains uniform regardless of the differences in the flavor used. I am biased, and maybe need a bit more time until this will clear in my head.

I am curious what do you think about that?

[egel]

One additional portion I noticed that could be useful for the users is to differentiate/emphasize the colors from the surroundings.

Here is a comment where the colors are not visually standing out. #21 (comment)