Add Kanagawa theme

[ScribeAwoken]

New Preset: Kanagawa

Since it's a popular terminal theme that felt oddly missing from the available presets, I decided to make a Kanagawa theme.

Also worth noting: I was not able to add the raw url to presets.json, since that file doesn't seem to exist in the repo.

Description

A dark theme based on rebelot's Kanagawa neovim color scheme.

Palette

@rebelot's Kanagawa color scheme for Neovim.

Screenshots (optional)

Wallpaper

I feel like the Hokusai print that gave the theme its name would be the most fitting choice of background here.

Checklist

Before submitting the PR, I checked:

• [x] I've only modified one preset
• [ ] I've added the URL to my raw preset in presets.json
• [x] I've checked the format of each json files I modified
• [x] (optional) I've added screenshots
• [x] The preset name is following preset naming guidelines.

Publication

• [x] I want to add my preset in the preset list.

Thanks for your submission we will review and merge it as quick as possible.