Set description to be markdown

Set `long_description_content_type` to be `text/markdown`

Author: pbashyal-nmdp

setup.py

@@ -45,6 +45,7 @@
     version='0.7.0',
     description="ARD reduction for HLA with Python",
     long_description=readme + '\n\n' + history,
+    long_description_content_type="text/markdown",
     author="CIBMTR",
     author_email='[email protected]',
     url='https://github.com/nmdp-bioinformatics/py-ard',