Switch to recommonmark for md to rst conversion

See also https://www.sphinx-doc.org/en/master/usage/markdown.html

Author: orangecms

Diff for: .travis.yml

@@ -3,7 +3,7 @@ python: 3.7
 install:
 - pip install Sphinx
 - pip install git+https://github.com/bashtage/sphinx-material
-- pip install m2r2
+- pip install recommonmark
 script: skip
 deploy:
 - provider: script

Diff for: conf.py

@@ -29,7 +29,13 @@
 # Add any Sphinx extension module names here, as strings. They can be
 # extensions coming with Sphinx (named 'sphinx.ext.*') or your custom
 # ones.
-extensions = ['m2r2', 'sphinx_material']
+extensions = ['recommonmark', 'sphinx_material']
+
+# see https://www.sphinx-doc.org/en/master/usage/markdown.html
+source_suffix = {
+    '.rst': 'restructuredtext',
+    '.md': 'markdown',
+}
 
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ['_templates']