Add unocss-preset-mgplus: UnoCSS preset for the mgplus mini CSS library

[Copilot]

Introduces unocss-preset-mgplus, a UnoCSS preset that brings mgplus styles into UnoCSS workflows — eliminating the need for a separate CSS import while enabling tree-shaking on utility classes.

Package setup

• package.json / tsconfig.json / tsup.config.ts — TypeScript library project with dual ESM+CJS output and type declarations; unocss as peer dependency
• test/preset.test.ts — 44 vitest tests covering all rule categories and preflight options

Preset implementation (src/)

• index.ts — exports presetMgplus(options?) accepting components, utilities, and darkMode flags
• types.ts — PresetMgplusOptions and ComponentName union type
• preflights.ts — injects CSS custom properties (:root { --mg-* }) and full component styles (button, badge, alert, nav, modal, grid, tabs, check, toggle, dropdown, loader, progress, group, icon, timeline, dark mode) as UnoCSS preflights; component inclusion is configurable
• rules.ts — tree-shakeable UnoCSS rules for all utility classes: spacing (mg-pad*, mg-marg*), sizing (mg-w*, mg-h*, mg-min-*, mg-max-*), display, overflow, visibility, border/radius, positioning, z-index, text, and color utilities (mg-{color}, mg-bg-{color}, mg-border-{color})

Usage

// uno.config.ts
import { defineConfig } from 'unocss'
import { presetMgplus } from 'unocss-preset-mgplus'

export default defineConfig({
  presets: [
    presetMgplus({
      components: ['button', 'badge', 'grid'], // or true for all
      utilities: true,
      darkMode: true,
    }),
  ],
})

Component styles with pseudo-classes/nested selectors are injected via preflights (no tree-shaking); utility classes are defined as UnoCSS rules and are tree-shaken at build time.