feat: add breaking change section

[SMoraisAnsys]

Adds checking for breaking change in the PR title and body. On repos following conventionnal commits, this will greatly help:

• users to know what breaking changes are introduced in a specific version;
• developers to have an idea of how often they are breaking their API.

I think that this could be used as a metric to know whether a repo is ready to move to version 1.0.0.

Extra change: reordering of the towncrier types to a (very) subjective priority list. Seems that the order in which the changes are displayed is following the pyproject.toml / towncrier.toml file data.

Close #722

Follow up of #810

---

Working tests performed:

• pr title with breaking change
• pr body with breaking change
• release

The release only contains one of the PR (I forgot the other) and does not contain the reordering which was performed in this PR

[SMoraisAnsys]

Updating title with "!" to verify the label change

[SMoraisAnsys]

Success. Changing back to feat: .... and adding "Breaking Change: ...." into the PR body

[SMoraisAnsys]

Modifying the PR content

[jorgepiloto]

Why are we checking the body of the pull-reques? I thought we were checking only its title.

[SMoraisAnsys]

Why are we checking the body of the pull-reques? I thought we were checking only its title.

We could restrict this kind of checking to the title only. However, the current changes align with the conventional commit convention which also checks for breaking change footer. This is related to git trailers but I don't think we should go through all the commits of a PR to check if a commit contains a breaking change. Since most of the repo merge the PR description into main, I think it make more sense to only check the PR title and body.