feat: add option for signing commits

[Yokozuna59]

I'd like to suggest adding two checkboxes that allow users to sign commits with:

1. 'Signed-off-by:' using git commit --signoff or git commit -s for short form.
2. GPG Sign using git commit --gpg-sign or git commit -S for signing with gpg key.
   Or without it using git commit --no-gpg-sign

---

As far as I know, these is an option called commit.gpgSign has boolean value indicating the default option for gpg signing commit. There isn't an option for signoff in git. But, there's one in VSCode git.alwaysSignOff which also has boolean value.

[bendera]

Good idea, I've added it to my TODO list.

[Yokozuna59]

Good idea, I've added it to my TODO list.

Thanks for your great work!