Initialize TypeScript NumPy-style core API for vector ops

[Copilot]

This PR establishes numpst as a TypeScript implementation of core NumPy-like array/vector primitives. It introduces a small, typed baseline API for construction, elementwise math, and reductions.

• TypeScript package scaffold

  • Added project setup (package.json, tsconfig.json) and build output typing/declarations.
  • Configured module entrypoints for compiled artifacts.

• NumPy-style API surface

  • Added src/index.ts with:
    • Constructors: array, zeros, ones, arange
    • Elementwise ops: add, subtract, multiply, divide
    • Reductions: sum, mean
  • Included shape checks for binary vector ops and guardrails for invalid inputs (e.g., zero step, empty mean).

• Docs and usage framing

  • Updated README with concise API list and project purpose.
  • Added .gitignore for generated/build dependency artifacts.

• Focused behavior coverage

  • Added targeted tests for constructor helpers, vector arithmetic, and reductions.

import { arange, add, mean } from "numpst";

const x = arange(5);          // [0, 1, 2, 3, 4]
const y = add([1, 2], [3, 4]); // [4, 6]
const m = mean([1, 2, 3, 4]);  // 2.5

Original prompt

TypeScript port of NumPy