Add docs

mkdocs.yml

@@ -0,0 +1,9 @@
+site_name: "mailcow: dockerized"
+repo_url: https://github.com/andryyy/mailcow-dockerized/
+remote_branch: master
+theme: readthedocs
+pages:
+    - 'Overview': 'index.md'
+    - 'Installation': 'install.md'
+    - 'First Steps': 'first_steps.md'
+    - 'Usage & Examples': 'u_and_e.md'