add py.typed

setup.py

@@ -6,7 +6,10 @@ from setuptools import setup
 
 if __name__ == "__main__":
     try:
-        setup(use_scm_version={"version_scheme": "no-guess-dev"})
+        setup(
+            package_data={"espec_pr3j": ["py.typed"]},
+            use_scm_version={"version_scheme": "no-guess-dev"},
+        )
     except:  # noqa
         print(
             "\n\nAn error occurred while building the project, "