feat: Support for JSON data parsing in latest version

[BradStaton]

Some projects post their various release channels as a single JSON document. I'd like to be able to parse that JSON data for the latest version in the same way I can for deployed versions.

For example, the k3s project's releases are listed at https://update.k3s.io/v1-release/channels, and I'd like to only retrieve the .data from the id=stable element.

Currently I track k3s releases from their GitHub page, but the latest and stable releases are indistinguishable from that page.

Describe the solution you'd like
Support for parsing JSON in latest version config similar to deployed version config

[JosephKav]

For k3s stable, you could do

  k3s-io/k3s (stable):
    latest_version:
      type: url
      url: https://update.k3s.io/v1-release/channels/stable
      url_commands:
        - type: regex
          regex: <title>Release v([^ ]+)

I'll need to add in support for some sort of filtering to get it to handle id=stable as deployed version's currently just handle plain JSON lookups, e.g. data[0].latest