feat(themes): add modus vivendi theme(s)

[matoous]

Add themes based on the dark variants of the modus themes (built-in with Emacs). This PR goes in line with #8728 and implements modus vivendi (dark) theme; reusing the original color palette.

modus_vivendi

modus_vivendi_tritanopia

modus_vivendi_deuteranopia

modus_vivendi_tinted

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See Modus Themes Pictures for original.

Potentially more themes could be added in the future: https://protesilaos.com/emacs/ef-themes

[atahrijouti]

Thank you for Prot's great themes. I've been craving Ef-themes and was looking into implementing them, would you happen to know if the structure is the same as modus operandi and vivendi?

[matoous]

@atahrijouti looking at https://github.com/protesilaos/ef-themes/blob/main/ef-dark-theme.el they should have the same structure. I tried it out here: https://github.com/matoous/helix/tree/md/ef-themes. Result:

It might need some more adjustments. For example bg-paren-match highlight is missing but used by the modus themes.

[atahrijouti]

That's really cool. Thanks :-)

[the-mikedavis]

Could you add the license for these (https://protesilaos.com/emacs/modus-themes#h:b14c3fcb-13dd-4144-9d92-2c58b3ed16d3) following the new notes from #8861? That should make it easier to package downstream (fedora for example)

[matoous]

@the-mikedavis added, thanks! I missed that.

[the-mikedavis]

Is it possible to cut down on the duplication by using theme inheritance? It looks like most of the color names are the same so the variants could inherit the base theme and change the palette. See the gruvbox themes for an example

[matoous]

@the-mikedavis done, thanks.

[saccarosium]

I would advocate to define also the highlights for the bufferline:

"ui.bufferline" = { bg = "bg-tab-bar" }
"ui.bufferline.active" = { bg = "bg-tab-current", fg = "fg-mode-line-active" }

[matoous]

@saccarosium updated, thanks!