List Python 3.8 and 3.8 too in the project classifiers

setup.py

@@ -64,6 +64,8 @@ setup(
     },
     classifiers=[
         "Programming Language :: Python :: 3.7",
+        "Programming Language :: Python :: 3.8",
+        "Programming Language :: Python :: 3.9",
         "Programming Language :: Python :: 3 :: Only",
         "License :: OSI Approved :: Mozilla Public License 2.0 (MPL 2.0)",
     ],