Add possibility to pass secrets via files

[britter]

Resolves #30

[britter]

Tested this in my homelab and it looks like it's working.

[britter]

@cromefire I addressed the two code comments.

Also the docker samples in the readme should be updated accordingly to make use of secrets.

I don't use docker that much so I don't exactly know how to pass secrets via files. Would you mind adding this yourself on top of my changes?

[cromefire]

Yeah was planning to, but I probably won't get to it today, I'll try and add it in the coming days, when I test it locally anyways.

[britter]

Hey @cromefire did you have a chance to look into this yet? Would love to have a release with this included.

[cromefire]

No I didn't have any time to look at it or test it yet. Time's currently very scarce for me, I hope I do get to it in the next few days, but thanks for the reminder.

[britter]

Hey @cromefire I've given it a shot and added an example for how to use the new feature with docker compose secrets. Let me know what you think!

[cromefire]

v1.3.0 has been created, binaries are attached and containers are built