[BUG] npm package contains extra files

[rubiesonthesky]

Describe the bug

When looking at the code in npmjs.org (https://www.npmjs.com/package/danger?activeTab=code), you can see that there are a lot extra files that do not need to be included to the package. The size of danger is already big, so it would be nice to reduce the install size even a little bit.

Paths that could be added to .npmignore

• .github
• .eslintignore
• .eslintrc.json
• .gitattributes
• .pre-commit-config.yaml
• .prettierignore
• .release-it.json
• CHANGELOG.md
• CONTRIBUTING.md
• Dockerfile
• VISION.md
• tsconfig.spec.json

Total would be around 90 kB saved. It's not that much of the total size of 1.43 MB, but at least something.

[orta]

Seems reasonable to me

[talentlessguy]

instead of npmignore I suggest files in package.json instead. npmignore is known for causing issues