Make typing_extensions only required for 3.7

Literal was introduced in Python 3.8.

hyfetch/types.py

@@ -1,3 +1,6 @@
+try:
+    from typing import Literal
+except ImportError:
     from typing_extensions import Literal
 
 AnsiMode = Literal['default', 'ansi', '8bit', 'rgb']

setup.py

@@ -38,7 +38,7 @@ setup(
     include_package_data=True,
     install_requires=[
         # Universal dependencies
-        'setuptools', 'typing_extensions',
+        'setuptools', 'typing_extensions; python_version < "3.8"',
         
         # Windows dependencies
         'psutil ; platform_system=="Windows"',