os-git-backup: add a way to avoid some conf changes that don't need backup

• I have read the contributing guide lines at https://github.com/opnsense/plugins/blob/master/CONTRIBUTING.md
• I have searched the existing issues, open and closed, and I'm convinced that mine is new.
• When the request is meant for an existing plugin, I've added its name to the title.

Is your feature request related to a problem? Please describe.
Hi, I installed os-git-backup and it works very well but :

I'm using os-nginx that has a honeypot feature that create a banned ip list in firewall alias rules
these changes are backed up and generate a lot of commits because it's a dynamic behavior
I'd like to avoid these hundreds commits

Describe the solution you'd like
I don't know how to prevent this behavior under the hood as an end user 😬
Perhaps some conf file that exclude some changes from being backed up

Start by reviewing the os-git-backup plugin and how os-nginx's honeypot updates firewall alias rules. Determine where backed-up configuration changes are selected, then define how an exclusion would be configured and verify that dynamic banned-IP changes no longer create repeated commits.