add stable_version as output in json.output

[cheese1]

currently we have per project:

{
"id": 13934,
"name": "ampache",
...
"version": "5.0.0-pre-release",
"versions": [
"5.0.0-pre-release",
"4.3.0",
"4.0.0-pre-release",
"3.5.1"
],
"stable_versions": [
"4.3.0",
"3.5.1"
],
...
}

would be great to have the latest stable_version as:
...
"version": "5.0.0-pre-release",
"stable_version": "4.3.0",
...

this would not break anyones scripts, as the meaning of version stays the same AND we get the possibility to filter for the latest stable version.

thanks

[cheese1]

@Zlopez analogue to the addition of stable_versions #753 but now just for the latest version

[Zlopez]

This sounds like a great idea. Thanks for the suggestion.