feat!: change release-it "hotfix" branch prefix

The hotfix- prefix used as a "magic branch name" for release-it was being used organically by engineers without intending to create releases. Rather than try to boil the ocean and change the instincts of each engineer, in #80 (closed) we agreed to change the prefix to release/fix-.

This is a breaking change since behaviour which worked previously now does not.

The change has been testing insofar as checking the regex syntax parses correctly. The change of prefix is such a minor change and the feature so little used that I'd not want to expend too much effort on it until #82 has been bottomed out.

Closes #80 (closed)