Replace `project/CompilerFlags` by `sbt-tpolecat` plugin

[guizmaii]

Hey guys,

I've seen that you're using your own defined scalac flags. Are you aware of the existence of https://github.com/DavidGregory084/sbt-tpolecat?

[sallareznov]

Hello @guizmaii , thank you for opening this issue.

Yes, we are using the sbt-tpolecat in every other project. except this one, oddly. @arthurteisseire , is there a particular reason why we're not using the plugin here?

[guizmaii]

Hey @sallareznov,

I opened a few other issues like this one in a few other CW open-source libs because the same CompilerFlags thing has been added when the libs have been updated to handle Scala 2.13.

I don't see any valid reason for the existence of this file since sbt-tpolecat is doing the same but in a better, open-source, maintained by the community way.