Improve domain matching to reduce false positives

[maximbaz]

@erayd is this what you had in mind for #170?

I also added some comments because this logic becomes quite complex 🙂
(so complex I made a mistake when writing it, as seen in the git history)

Fixes #170

[erayd]

@maximbaz Almost. I don't think we should match for unknown TLD though. Is there a particular reason why we are doing that currently?

[maximbaz]

We support hostnames if they match exactly what's currently in the address bar (case 3 in my comment in the code, initially requested for pi.hole in #62 (comment) and implemented in #107), it seems natural that we also want to support subdomains for such entries (case 2 in my comment in the code, example of that would be if login.pi.hole is currently in the address bar and a user has a pi.hole.gpg pass entry).

In other words, the argument is consistency, if "github.gpg" shows up on "login.github.com", "pi.hole.gpg" should show up on "login.pi.hole".