Check for latest available checkmk version

[MarkusH]

ok found it here

Check if there's a new CheckMK version

Hey guys, I saw there are several posts here asking for a way to check if there is a new version of Checkmk available. @thl-cmk already created a plugin to do this, but that relies on the page checkmk.com/download. We can’t promise that the structure of that page never changes, in fact it did change this week when we released Checkmk 2.1.0. Because of this I have created a JSON file that contains the latest version of each of the major versions that we currently support. This file is being cre…

https://download.checkmk.com/stable_downloads.json is perfect.