Drop Python 3.7 from python_requires (#118)

Author: tianweidut

setup.cfg

@@ -27,7 +27,7 @@ packages = find:
 install_requires =
     dnspython>=2.0.0 # optional if deliverability check isn't needed
     idna>=2.0.0
-python_requires = >=3.7
+python_requires = >=3.8
 
 [options.package_data]
 * = py.typed