request: auto sign-off when commit use `melos version`

### Is there an existing feature request for this?

- [X] I have searched the existing issues.

### Command

_No response_

### Description

Add sign-off and GPG sign for commits.

### Reasoning

Signing a commit in git is a necessary thing to ensure that the commit was initiated by a validator.

### Additional context and comments

In commits, the command I often use is `git commit --signoff -S`
I wish there was an option added to `melos version`

Start by locating the melos version command and its commit-generation path. Check how command options are defined and how commits are created, then determine how sign-off and GPG signing should be exposed. Done means melos version supports the requested signing options and tests cover the resulting commit behavior.

Written by the indexing model from the issue text.