Better document Flogger's status (active, maintained, in use at Google)

Flogger team and users - we love this library.

Flogger has always felt like a hobbyist open-source initiative. However, lately, there's even less activity.
We need to pick our tools and changing a logging API can be painful.

We're curious if:
* this is effectively complete
* is it abandoned
* are there plans to move it to a new home (e.g. CNCF)
* what are other users thinking and alternatives, forks, etc.