Add readthedocs.yml

This PR adds settings for Read the Docs.

Author: koic

mkdocs.yml

@@ -0,0 +1,13 @@
+site_name: "A RuboCop extension focused on enforcing Rails best practices and coding conventions."
+repo_url: https://github.com/rubocop-hq/rubocop-rails
+edit_uri: edit/master/manual/
+copyright: "Copyright © 2012-2019 Bozhidar Batsov and RuboCop contributors"
+docs_dir: manual
+pages:
+- Home: index.md
+- Installation: installation.md
+- Usage: usage.md
+- Cops: cops.md
+- Cops Documentation:
+    - Rails Cops: cops_rails.md
+theme: readthedocs

readthedocs.yml

@@ -0,0 +1,5 @@
+build:
+    image: stable
+
+formats:
+    - htmlzip