Optional config option the SHLVL module

Feature Request

Is your feature request related to a problem? Please describe.

Not really, just I'm used as a programmer to begin counting with 0.

Describe the solution you'd like

According to the bash manual, the $SHLVL variable always begin with 1, and is incremented after other shell is opened.
But, as a programmer, I consider the first shell (that one I open manually) the number 0 (not 1).
So, I thinked and how about an option in SHLVL module the adjust this variable, like so adjust = -1 ?

Describe alternatives you've considered

No alternatives. This is a variable used in all shells, so we are not going to change it internaly.