Detect commit messages in the squashed commit

For example see https://github.com/bahmutov/generator-node-bahmutov/commit/8eb48addc834294f6248d163e69c37ef3ca38e12

The subject is just `Immutable (#57)` but the body has titles from 3 commits that were squashed from the pull request. One of them is semantic commit! Should detect such commits and return valid list

```
* feat(immutable): optional immutable linter, close #56

* add immutable to E2E answers

* add note to readme
```

No files or tests are named; start by locating the commit-message parsing or validation entry point and existing semantic-commit tests. Use the supplied squashed commit body as a fixture; done means returning a valid list that includes the semantic feat entry and the other commit titles.

Scritto dal modello di indicizzazione a partire dal testo della issue.