[feat] Add support for .gopass-audit-ignore

[ltecheroffical]

Backstory (Got a little carried away, skip to the real part if you don't want to read this):

A few months ago I made a issue for ignoring entries in .gopass-audit-ignore. That got a PR and the PR got accepted (Thanks), I moved to a different password manager and switched back to gopass. I then read some docs to use it better this time and then noticed that this repo doesn't have the .gopass-audit-ignore ignorance feature. I use this to ignore passwords I don't have control over or are forced to be weak (like when the account is just a number). When using this repo I noticed something, the .gopass-audit-ignore file was there but being ignored.

The real part:

The issue I posted on the gopass repo did get a PR and the PR got merged. But the feature never got implemented here. This should get implemented here for feature parody sake and to swap between the two easily.