ZIO: How to join Fibers for Processes that run forever

you don't have to .join fiber if they run forever.

Note that since 1.0.0-RC17, #zio added the .daemon combinator for exactly that reason, see release note here: https://github.com/zio/zio/releases/tag/v1.0.0-RC17 and that from now on, .fork should be avoided for forever-running fibers.