Add executable to package definition

ga.cabal

@@ -32,14 +32,22 @@ library
                      , SS19
 
 
--- executable GA-PFP
+executable ga
---   build-depends:       base ^>=4.12.0.0
+  build-depends:       base ^>=4.12.0.0
---                      , monad-loops
+                     , MonadRandom
---                      , random-fu
+                     , monad-loops
---                      , protolude
+                     , random
---   default-language:    Haskell2010
+                     , random-fu
---   -- exposed-modules:
+                     , random-shuffle
---   hs-source-dirs:      src
+                     , protolude
---   main-is:             Main.hs
+                     , QuickCheck
---   -- other-extensions:
+                     , quickcheck-instances
---   -- other-modules:
+                     , text
+                     , protolude
+  default-language:    Haskell2010
+  hs-source-dirs:      src
+  main-is:             Main.hs
+  other-modules:       GA
+                     , Seminar
+                     , Pretty
+                     , SS19