Does not detect breaking change `!` properly

Thanks for the GitHub Action!

It seems it does not detect breaking change `!` properly.

Based on [Conventional Commits](https://www.conventionalcommits.org/en/v1.0.0/#commit-message-with-scope-and--to-draw-attention-to-breaking-change), the breaking change should be something like `feat(api)!: some changes`. 
However, right now even `feat!(api): some changes` passes.