Add minisign verification

[desttinghim]

Attempt to implement #67

I don't know enough about github actions and nodejs to actually test if my code worked.

[goto-bus-stop]

Thanks for the PR!

I think this will need some work, I can pick that up once I have time to review, as it's in my experience much easier to test an action when you own the repo... It's already very helpful to just have the minisign API calls in there. I'll try to do so this week but can't promise much given my schedule at the moment.

[desttinghim]

Thanks for the prompt response! :)

I learned a bit since I made the PR. First, I figured out I needed to run npm run prepare for my changes to have an impact. Second, I realized the minisign library relies on sodium-native. This is probably fine, but it will take me a bit more time to figure out how to get all the dependencies to npm install on my nixos development machine.

[desttinghim]

Closing this version of the PR in favor of #74