Set description content type

Signed-off-by: Stephen Gallagher <[email protected]>

Author: sgallagher

setup.py

@@ -27,6 +27,7 @@
     author_email='[email protected]',
     description='Tools for working with translations of modulemd',
     long_description=long_description,
+    long_description_content_type='text/markdown',
     # ModulemdTranslationHelpers also requires koji and libmodulemd which
     # are not available on PyPI and must be installed separately. On Fedora,
     #  this is done with `dnf install koji libmodulemd`