build: only publish required files

• Integration MR: gitlab!26298 (closed)

This adds a files field to the package.json to prevent us from publishing unnecessary files along with the compiled bundles.

Files being published before this change

• bin
• dist
• doc
• documentation
• lib
• scss_to_js
• src
• .dependency_url
• .eslintignore
• .eslintrc.yml
• .stylelintrc
• CHANGELOG.md
• CONTRIBUTING.md
• Dockerfile
• FAQ.md
• LICENSE
• Makefile
• README.md
• babel.config.js
• charts.js
• documentation.js
• gitlab-ui.master.tgz
• index.js
• package.json
• utils.js
• config.js

Files being published after this change

• README.md
• package.json
• LICENSE
• dist
• CHANGELOG.md
• src
• scss_to_js
• documentation
• documentation.js
• index.js
• charts.js
• utils.js
• config.js

As per NPM's documentation:

Certain files are always included, regardless of settings:

• package.json
• README
• CHANGES / CHANGELOG / HISTORY
• LICENSE / LICENCE
• NOTICE
• The file in the “main” field