Automatically guess change level of a commit/PR

[fizruk]

We can at least spot fixes by "fix" keyword in commit message.

We can also look out for words like

• "breaking change"
• "minor"

We can also look at files with certain extensions :

• changes to *.md, *.rst and such are probably just documentation changes
• changes to hidden files (with leading dot) are probably not relevant to the project's logic/API.

[fizruk]

We can actually formalise these rules in .changelogged.yaml and have users be able to overload default ones.

[viviag]

It's usable only for few versioning strategies. So it's arguable.