MAINT: Fix long_description

Author: mgxd

setup.cfg

@@ -11,8 +11,8 @@ classifiers =
     Programming Language :: Python :: 3.8
 description = NeuroImaging Babies provides processing tools for magnetic resonance images of the brain in infants.
 license = Apache License, 2.0
-long_description = file:README.rst
-long_description_content_type = text/x-rst; charset=UTF-8
+long_description = file:README.md
+long_description_content_type = text/markdown; charset=UTF-8
 project_urls =
     GitHub = https://github.com/nipreps/nibabies
 url = https://github.com/nipreps/nibabies