Added scalafmt, scalafix and github ci as suggested in...

.github/workflow/ci.yml

.scalafix.conf

.scalafmt.conf

README.md

build.sbt

project/plugins.sbt

src/main/scala/Example.scala

src/main/scala/lisa/KernelHelpers.scala

src/main/scala/lisa/kernel/Printer.scala

src/main/scala/lisa/kernel/fol/CommonDefinitions.scala

src/main/scala/lisa/kernel/fol/EquivalenceChecker.scala

src/main/scala/lisa/kernel/fol/FOL.scala

src/main/scala/lisa/kernel/fol/FormulaDefinitions.scala

src/main/scala/lisa/kernel/fol/Substitutions.scala

src/main/scala/lisa/kernel/fol/TermDefinitions.scala

src/main/scala/lisa/kernel/fol/TermLabelDefinitions.scala

src/main/scala/lisa/kernel/proof/Judgement.scala

src/main/scala/lisa/kernel/proof/RunningTheory.scala

src/main/scala/lisa/kernel/proof/SCProof.scala

src/main/scala/lisa/kernel/proof/SCProofChecker.scala