Add pre* change types by default

[ecraig12345]

There are additional change types prepatch, preminor, premajor which beachball doesn't fully support today. Making these available by default outside of a major version bump would be perceived as a breaking change, but we should consider adding them in the next major version.

(As of #944, beachball will allow these change types if specified with --type on the command line, by editing the change files, or with a custom change type prompt. But they won't show up in the change type prompt by default.)