add exectuable sources

exec/Main.hs

@@ -0,0 +1,5 @@
+module Main where
+
+main :: IO ()
+main = do
+    putStrLn "There is no WASM!"

package.yaml

@@ -31,6 +31,15 @@ library:
   - containers           >= 0.5  && <0.6
   - utf8-string          >= 1.0
 
+executables:
+  wasm:
+    source-dirs: exec
+    main: Wasm.hs
+    dependencies: 
+    - wasm == 0.1.0
+    - base
+    - optparse-applicative
+
 tests:
   test:
     main: Test.hs

wasm.cabal

@@ -50,6 +50,14 @@ library
       Paths_wasm
   default-language: Haskell2010
 
+executable wasm
+  main-is: Main.hs
+  hs-source-dirs: exec
+  build-depends:
+      base >=4.6 && <5.0
+    , wasm ==0.1.0
+    , optparse-applicative >= 0.13
+
 test-suite test
   type: exitcode-stdio-1.0
   main-is: Test.hs