Draft: Inline links + change type whitelisting
For our application, we use inline version links. They are not in conflict with KeepAChangelog so I added support for parsing them as well.
Second change we needed is to remove the whitelist of change types. There are discussions in the KeepAChangelog repo about adding new ones (e.g. Dependencies) + we need the section names in other languages. To accommodate both, I've relaxed the requirements to just "a single word second-level heading".