Upgrade to CE3/FS2 3

[keynmol]

I was quite surprised to find out that Almond uses fs2 :) https://github.com/almond-sh/almond/blob/master/modules/shared/interpreter/src/main/scala/almond/interpreter/input/InputHandler.scala

Makes sense, when I think about it.

Would it be possible to either

1. Upgrade to 3.x lineage of FS2
2. Remove fs2 as a dependency

I only spotted it because I wrap almond in a project that uses CE, and that blocks the upgrade to CE3.

Will happily PR an upgrade to FS2 3.x as long as there's agreement, less certain about what removing fs2 would involve.

WDYT @alexarchambault ?