Whitelist files to include when publishing

[MrChocolatine]

Build

Whitelist files to include when publishing (#25)

To reduce the final bundle size.

Before

➜ npm publish --dry-run

npm notice === Tarball Contents ===
npm notice 163B  .github/CODEOWNERS
npm notice 90B   config/environment.js
npm notice 192B  index.js
npm notice 463B  addon/helpers/reading-time.js
npm notice 80B   app/helpers/reading-time.js
npm notice 2.8kB package.json
npm notice 1.1kB LICENSE.md
npm notice 2.3kB README.md
npm notice 313B  .github/workflows/ci.yml
npm notice 375B  .github/workflows/contributors.yml
npm notice 691B  .github/dependabot.yml
npm notice 547B  .github/workflows/tag-release-publish.yml
npm notice === Tarball Details ===
npm notice name:          ember-reading-time
npm notice version:       2.0.0
npm notice package size:  3.8 kB
npm notice unpacked size: 9.1 kB
npm notice total files:   12

After

➜ npm publish --dry-run

npm notice === Tarball Contents ===
npm notice 90B   config/environment.js
npm notice 192B  index.js
npm notice 463B  addon/helpers/reading-time.js
npm notice 80B   app/helpers/reading-time.js
npm notice 2.9kB package.json
npm notice 1.1kB LICENSE.md
npm notice 2.3kB README.md
npm notice === Tarball Details ===
npm notice name:          ember-reading-time
npm notice version:       2.0.0
npm notice package size:  2.9 kB
npm notice unpacked size: 7.1 kB
npm notice total files:   7