Add documentation about the `password-cli` (#83)

[blackheaven]

A bit of documentation, let me know if you had something else in mind.

[blackheaven]

I don't think the CI failure is related to my PR.

[Vlix]

Ah, yes. optparse-applicative has a newer version we can probably allow.

Not sure if I like the repetition of the Testing segment in all the modules. But then again, it's good information close to the usage site of the library. I might have to think about it a bit more.

[Vlix]

Ah, nevermind. I've literally asked for that in the #83 issue. 🤦

I would like to also see the second part of the checkboxes of the issue's first post ticked in this PR: Mostly changing the "SOME-HASH" sections in the password-cli/README to 'SOME-HASH' and adding a comment that using " might interpolate in some cases (e.g. when a hash or password has a $ in it)

[blackheaven]

Ah, nevermind. I've literally asked for that in the #83 issue. 🤦

I would like to also see the second part of the checkboxes of the issue's first post ticked in this PR: Mostly changing the "SOME-HASH" sections in the password-cli/README to 'SOME-HASH' and adding a comment that using " might interpolate in some cases (e.g. when a hash or password has a $ in it)

Done :)

[blackheaven]

@Vlix can you have another look please?

[blackheaven]

@Vlix thanks for you feedback, ready for a new review.