[Feature Request] Configurable ruler for the commit message field

[gknapp]

It would be helpful if a vertical ruler could be shown in the commit message box. Typically at 72 or 80 characters (or make this configurable in settings).

This can help some teams who stick to this convention. At present I use VSCode as my commit editor, where I can configure these vertical rulers.

[love-linger]

Commit message box does not use monospace font... It's hard to calculate the x-position of vertical ruler.