Support for filtering merge commits

[anthonyoteri]

Is your feature request related to a problem? Please describe.
I have the Pull Requests: Merge Commits title set to use the PR title instead of the default message. On branches with a single commit, the default title for the PR is the same as the single commit. This leads to 2 commits with the same message in the main branch, which then gets picked up by this action and I get duplicate entries in the changelog. One entry for the regular commit, and one for the merge commit.

A clear and concise description of what the problem is. Ex. I'm always frustrated when [...]
See above.

Describe the solution you'd like
It would be good to have some kind of configuration option in the config file to filter merge commits so that these duplicates can be avoided.

Describe alternatives you've considered
Manually editing the release notes after release, which is a workaround at best.