Merge branch '1.12' into 1.13

* 1.12:
  [Docs] Fix readthedocs configuration files
  [Docs] Add links to 2.x docs

docs/_themes/sylius_rtd_theme/layout.html

@@ -99,6 +99,7 @@
       </div>
 
       <div class="wy-menu wy-menu-vertical" data-spy="affix" role="navigation" aria-label="main navigation">
+        <a href="https://docs.sylius.com/" target="_blank"><b>📖 2.0 Documentation</b></a>
         {% set toctree = toctree(maxdepth=2, collapse=False, includehidden=True) %}
         {% if toctree %}
             {{ toctree }}

docs/_themes/sylius_rtd_theme/versions.html

@@ -9,6 +9,7 @@
     <div class="rst-other-versions">
       <dl>
         <dt>Versions</dt>
+          <dd><a href="https://docs.sylius.com/">2.0</a></dd>
         {% for slug, url in versions %}
           <dd><a href="{{ url }}">{{ slug }}</a></dd>
         {% endfor %}