chore(CHANGELOG): add an extra new line after each item in the "BREAKING CHANGES" list

This ensures that the next item will appear on a new line and be properly
parsed as new list item (and not as the continuation of the current item),
even if the current item does not end with a newline character.
Currently, it would result is something like this:

    - **item 1**: due to ...
      blah1 blah1 blah1- **item 2**: due to...
      blah2 blah2 blah2

instead of the intended:

    - **item 1**: duo to ...
      ...
    - **item 2**: due to ...
      ...