Bump diff compares exact pull request changes only

This new release mostly includes a bugfix on the automated diff feature on pull requests.

🐛 Bug fix

• The automatic bump diff action will now only compare the exact changes made in your pull request, by ignoring any merge commit (GitHub automatically runs any Github-Action on a merge commit between your PR and your target branch), and checking the last common ancestor between your target branch and your PR head branch. This is hopefully the last bugfix around diff management in our github-action. Sorry to those of you who have been (patiently) sharing their issues, and especially @gmourier from Meilisearch 🙏

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