Set up GitHub Packages auto publish

[claude]

Closes #22

What's in this PR

package.json — adds publishConfig pointing at the GitHub Packages npm registry. This is the only change I can push (the GitHub App token lacks workflows permission for workflow files).

One manual step needed

After merging, add this file to your local clone and push to main:

.github/workflows/publish-to-github-packages.yaml

name: Publish to GitHub Packages

on:
  push:
    tags:
      - "v*"

jobs:
  publish-to-github-packages:
    runs-on: ubuntu-latest
    permissions:
      contents: read
      packages: write

    steps:
      - name: Checkout
        uses: actions/checkout@v4

      - name: Setup Node.js
        uses: actions/setup-node@v4
        with:
          node-version: "20"
          registry-url: "https://npm.pkg.github.com"
          scope: "@chriscalo"

      - name: Install dependencies
        run: npm ci

      - name: Publish
        run: npm publish
        env:
          NODE_AUTH_TOKEN: ${{ secrets.GITHUB_TOKEN }}

To release after setup

npm version patch   # or minor / major
git push --follow-tags

The workflow fires on any v* tag and publishes to GitHub Packages automatically. No build step — @chriscalo/file is plain JS.