Add root TypeScript exports while preserving explicit stylesheet imports

[Copilot]

This updates maltipoo from a stylesheet-only package to a dual-purpose package: root imports now resolve to a JS/TS module for shared constants, while compiled CSS remains available via explicit stylesheet subpaths. Existing dist/stylesheets outputs are preserved, and package exports now define the supported import surface directly.

• Package entrypoints

  • Change the package root to resolve to dist/index.js with dist/index.d.ts typings
  • Add explicit exports for stylesheet assets:
    • maltipoo/stylesheets/doi.css
    • maltipoo/stylesheets/doi.min.css
  • Preserve compatibility for explicit legacy paths under maltipoo/dist/stylesheets/*

• TypeScript constants

  • Add a minimal src/index.ts entrypoint
  • Export initial named constants derived from existing DataCite brand colors:
    • DATACITE_PRIMARY_DARK_BLUE
    • DATACITE_PRIMARY_LIGHT_BLUE

• Build output

  • Add a TypeScript build step that emits:
    • dist/index.js
    • dist/index.d.ts
  • Keep the existing Sass/PostCSS stylesheet build unchanged in output location:
    • dist/stylesheets/doi.css
    • dist/stylesheets/doi.min.css

• Documentation

  • Update the README to show:
    • root constant imports from maltipoo
    • stylesheet imports from maltipoo/stylesheets/doi.min.css
    • continued availability of explicit dist/stylesheets imports

Example usage:

import {
  DATACITE_PRIMARY_DARK_BLUE,
  DATACITE_PRIMARY_LIGHT_BLUE,
} from "maltipoo";

import "maltipoo/stylesheets/doi.min.css";