chore(bootstrap-4): add repo to package.json

[abemedia]

Reasons for making this change

Without the repo in the package docs tooling like Mend Renovate is not able to find release notes or join the multiple packages into a single update PR.

Checklist

• I'm updating documentation
  • I've checked the rendering of the Markdown text I've added
• I'm adding or updating code
  • I've added and/or updated tests. I've run npm run test:update to update snapshots, if needed.
  • I've updated docs if needed
  • I've updated the changelog with a description of the PR
• I'm adding a new feature
  • I've updated the playground with an example use of the feature