Add transparent theme based on base16_default

[GreasySlug]

related #3059
discussions #3142
It was created based on the base16_default theme, and matches especially dark images.
The drawback is that the background is all transparent, making it hard to see pop-ups.
The pop-up background can be black for better visibility, but I don't do that.

[the-mikedavis]

You may want to add a ui.cursorline.primary and maybe a ui.cursorline.secondary theme for cursorline. Otherwise this looks good to me 👍

[the-mikedavis]

Did you mean to update the ui.cursor and not ui.cursorline scopes in that commit? Not defining cursorline is ok if it wouldn't look good in the theme anyways but it's worth giving it a try even if you won't use the feature

[GreasySlug]

Oh, sorry, I took mistook cursorline for cursor.
However, I tried to add them, but the default colors were inevitably too intense, so I gave up adding them.
I would like to add them when I can change the transparency in helix.

[the-mikedavis]

I don't think real transparency is possible because of terminal limitations, although there is similar work like dimming #2751

[the-mikedavis]

👍 🎨

Could you add a screenshot to the themes wiki? https://github.com/helix-editor/helix/wiki/Themes