Allow hyphens to be optional in prereleases

[guzman-raphael]

Fix #38

[mindsers]

Does this PR passes unit tests?

[mindsers]

@guzman-raphael Hey, I looked again at this PR and one thing we need to take care is the validation feature.

The Action validates the format of the changelog's entries base on Semantic Versioning, but allowing other versioning format might break the validation checks.
Either we should ensure if validations checks are still working when using other formats, or we should deactivate the validation checks when the Action detect it is not valid SemVer.