MNT: Add classifiers to improve PyPI listing

Author: effigies

setup.cfg

@@ -5,6 +5,20 @@ description = HCP version of Gradient Unwarping Package for Python/Numpy
 author = Human Connectome Project
 long_description = file:README.md
 long_description_content_type = text/markdown
+classifiers =
+  Development Status :: 6 - Mature
+  License :: OSI Approved :: MIT License
+  Programming Language :: Python :: 2.7
+  Programming Language :: Python :: 3.6
+  Programming Language :: Python :: 3.7
+  Programming Language :: Python :: 3.8
+  Programming Language :: Python :: 3.9
+  Programming Language :: Python :: 3.10
+  Programming Language :: Python :: 3.11
+  Programming Language :: Python :: 3.12
+  Operating System :: OS Independent
+  Topic :: Scientific/Engineering :: Image Processing
+  Topic :: Scientific/Engineering :: Medical Science Apps.
 
 [options]
 packages = find: