Add support to changelog-draft for non-squash merge strategies

还没有人认领这个 Issue。

We're currently looking up a commit's associated PR by searching for a PR with a matching `merge_commit_sha` field. This works well for squash-merged PRs, but in other cases, it leaves us with a bunch of unassociated commits (i.e. the ones that aren't the merge commit or the head of the rebased-and-ff-merged branch).

首先定位使用 merge_commit_sha 搜索 pull request 的 changelog-draft 代码，然后追踪相关提交是如何收集的。检查 GitHub pull request 数据以及涉及的合并策略。完成的标准是，非 squash 合并不再留下未关联的适用提交；如果项目有针对这一行为的测试，请添加或更新覆盖范围。

由索引模型根据 Issue 内容生成。