fix(day)!: Chose palette for day

[gi1242]

Thanks for creating this color scheme. I recently started using treesitter and found this colorscheme very helpful.

I did, however, find the day colors washed out. I like having a bright background (#ffffff) during the day; to do this I have to set day_brightness = 0, and in that case the colors are all washed out and too similar. Looking at the code, it looks like in day mode you just invert colors of the night palette and then increase the lightness if it is too dark. I couldn't find a clean elegant way to fix it so that foreground colors stay dark but are more vibrant.

Instead, I just manually inverted the colors and played with the saturation / lightness so that it was vibrant enough. With a manually chosen palette the day_brightness setting isn't needed anymore, so I removed it. (Technically the invert_colors and invert_highlights functions aren't needed either.)

Feel free to merge this if you like it.

Personally I use

fg=#000000
terminal_black=#000000
bg=#ffffff

but I let the defaults be softer colors obtained by inverting the night palette.