Web of Trust

I want to implement this feature from the README:

Vouch lists can also form a web of trust. You can configure Vouch to read other project's lists of vouched or denounced users. This way, projects with shared values can share their trust decisions with each other and create a larger, more comprehensive web of trust across the ecosystem. Users already proven to be trustworthy in one project can automatically be assumed trustworthy in another project, and so on.

I think the cleanest way to do this is:

• Allow all our Nu functions to take a list of vouch files (in priority order).
• Add a GitHub action that downloads and syncs a set of remote vouch files (via HTTP)
• Add a param to our existing check action(s) to take a directory of vouch files (loaded in filesystem sort order).
• Our own vouch file should always take top priority

Start with the README section describing web-of-trust vouch lists, then inspect the Nu functions and existing check actions mentioned in the issue. Define how priority works for multiple files, how remote files are synchronized, and how directory ordering is applied. Done means local and remote vouch lists can be combined while the project's own file remains highest priority.