[+] Add numpy optional dependency

setup.py

@@ -33,6 +33,9 @@ setup(
     package_data={'hyfetch': ['hyfetch/*']},
     include_package_data=True,
     install_requires=['setuptools', 'typing_extensions'],
+    extras_require={
+        'Gradient color_scale': ['numpy']
+    },
     entry_points={
         "console_scripts": [
             "hyfetch=hyfetch.main:run",