runner-images/images/linux/toolset-1804.json

{
    "toolcache": [
        {
            "name": "Python",
            "url" : "https://raw.githubusercontent.com/actions/python-versions/master/versions-manifest.json",
            "platform" : "linux",
            "platform_version": "18.04",
            "arch": "x64",
            "versions": [
                "2.7.*",
                "3.5.*",
                "3.6.*",
                "3.7.*",
                "3.8.*"
            ]
        },
        {
            "name": "node",
            "url" : "https://raw.githubusercontent.com/actions/node-versions/master/versions-manifest.json",
            "platform" : "linux",
            "arch": "x64",
            "versions": [
                "8.*",
                "10.*",
                "12.*",
                "14.*"
            ]
        }
    ]
}