feat!: support Tailwind v4

[unseen-ninja]

This PR aims to provide a semi-automatic SASS-based build system to generate viable configs for Tailwind v4. (#19)

The current setup generates two distinct files.

1. shades.css is home to all of Catppuccin's colours and the different tints and shades tailwind expects. Tints and shades are only generated for each of the 14 accent colours.
2. tailwind.config.css then is the actual config tailwind uses. This builds on top of shades.css therefore it needs to be imported in your CSS structure!

The Tailwind config provides default colours for light and dark mode (set to be latte and mocha respectively) as well as flavour classes and custom variants for each of the four flavours.

In short a demo config file would look like this:

@import "tailwindcss";


/* from shades.css */
:root {
  --catppuccin-latte-mauve: #8839ef;
  --catppuccin-latte-base: #eff1f5;
  --catppuccin-frappe-mauve: #ca9ee6;
  --catppuccin-frappe-base: #303446;
  --catppuccin-macchiato-mauve: #c6a0f6;
  --catppuccin-macchiato-base: #24273a;
  --catppuccin-mocha-mauve: #cba6f7;
  --catppuccin-mocha-base: #1e1e2e;
}



/* from tailwind.config.css */
@theme inline {
  --color-ctp-mauve: var(--catppuccin-mauve);
  --color-ctp-base: var(--catppuccin-base);
}


@layer base {
  :root {
    --catppuccin-mauve: var(--catppuccin-latte-mauve);
    --catppuccin-base: var(--catppuccin-latte-base);
    @variant dark {
      --catppuccin-mauve: var(--catppuccin-mocha-mauve);
      --catppuccin-base: var(--catppuccin-mocha-base);
    }
  }
  .latte {
    --catppuccin-mauve: var(--catppuccin-latte-mauve);
    --catppuccin-base: var(--catppuccin-latte-base);
  }
  .frappe {
    --catppuccin-mauve: var(--catppuccin-frappe-mauve);
    --catppuccin-base: var(--catppuccin-frappe-base);
  }
  .macchiato {
    --catppuccin-mauve: var(--catppuccin-macchiato-mauve);
    --catppuccin-base: var(--catppuccin-macchiato-base);
  }
  .mocha {
    --catppuccin-mauve: var(--catppuccin-mocha-mauve);
    --catppuccin-base: var(--catppuccin-mocha-base);
  }
}

[unseen-ninja]

This is how it could look in the end: https://play.tailwindcss.com/eYXckDj09D