Enable pulling releases from Forgejo-based services

[NezbednikSK]

This PR adds a host setting for the GitHub source, so services like Codeberg are supported as they have an API that's compatible w/ GitHub.

    "source": {
        "type": "github_release",
        "host": "https://codeberg.org",
        "format": "zip",
        "repository": "boreal/GRRLIB-Examples-Collection",
        "file": "release.zip"
    }