Investigate and possibly add support for Scala 3

[ColOfAbRiX]

Description

Scala is clearly moving towards the next version and Figlet4s wants to be an up to date library.

Do a spike for to investigate the effort required to support Scala 3 and produce a PoC. Consider using 2.13 libraries for Scala 3 too.

If the PoC is succesfully and the effort required it not too big (i.e. a week for production ready), extend the PoC to full feature.

Figlet4s needs to also support Scala 2.12 and 2.13 at the moment of writing

Status of the libraries as of 22/10/2021

Core libraries

• cats-core: supports Scala 3
• cats-effects: supports Scala 3
• enumeratum: does not support Scala 3 but not needed in Scala 3

Testing

• scalatest: supports Scala 3
• scalacheck: found a mention of Scala 3
• scalamock / mockito: do not support Scala 3, consider dropping it
• scalameter: does not support Scala 3, consider dropping it

SBT plugins

• scalafmt: supports Scala 3
• scalafix: limited support for Scala 3
• wartremover: supports Scala 3

Compiler

• compiler options: sbt-tpolecat provides some useful compiler flags
• linting: there seems to be very limited compiler linting