Prepare package for publishing to NPM

[ab-gnm]

What does this change?

This PR includes minimal changes to get the package ready for publishing on npm.

Changes include:

1. Added @guardian namespace to package name.
2. Moved publish-ignored files from bower.json/ignore to .npmignore
3. Updated install instructions in README.md to refer to npm instead of bower,
4. Removed bower.json

How to test

Update the package from npm: npm i @guardian/fence and ensure it correctly installs. Additional step: Update an existing repository that uses fence to fetch the dependency from npm, instead of directly from github/bower.

How can we measure success?

The dependencies provided by https://github.com/guardian/mobile-apps-article-templates/blob/master/package.json in https://github.com/guardian/android-news-app should start being available again in the TeamCity builds.

Have we considered potential risks?

Images

Accessibility

• [ ] Tested with screen reader
• [ ] Navigable with keyboard
• [ ] Colour contrast passed
• [ ] The change doesn't use only colour to convey meaning