fix: include code.json in distribution zipfile (#27)

* code.json needs to be in the zipfile for flopy's get-modflow --subset
* previously included by default, now need make-code-json --zip arg

scripts/build_programs.py

@@ -115,6 +115,8 @@ def run_cmd(args) -> bool:
             "-ad",
             str(path),
             "--verbose",
+            "--zip",
+            str(zip_path)
         ]
     ), "could not make code.json"
     assert zip_path.is_file(), "could not build distribution zipfile"