Add List date create of cache.json file to Action

[patsevanton]

I have idea how fix
#162
#159
#157
#156

1. check cache.json of []
2. run update for app with []

[patsevanton]

But need first know where store update -f

[leucos]

Thanks @patsevanton for the suggestion !
I finally fixed this in todays commits.

Basically, if the versions slice returned by the fetcher goroutine has zero length, it is simply ignored and the entry in the cache is not updated.
I also lowered the concurrency which seems to be the culprit in the action (although it works well locally with a GH token, go figure ¯_(ツ)_/¯).