Add label for automatic news-generation + bot

It could be cool to have labels on PR's that can be used to automatically generate news snippets with a bot.

For example, we could have two labels:

- Newsworthy
- Breaking

And when these labels are added, the title of the PR turns into a link on some web-page and people can check that website from time to time to check if their package is affected by some interesting change (e.g. removal of the static library).