Minor doc changes

- Add saythanks.io link
- Set lang="en" attribute in html tag

docs/_templates/layout.html

@@ -51,6 +51,9 @@
         <li class="nav-item">
           <a target="_blank" class="nav-link" href="https://github.com/instaloader/instaloader">GitHub</a>
         </li>
+        <li class="nav-item d-sm-none d-lg-block">
+          <a target="_blank" class="nav-link" href="https://saythanks.io/to/aandergr">Say Thanks!</a>
+        </li>
       </ul>
       <form class="form-inline" action="search.html" method="get">
         <div class="input-group my-2 my-sm-0 ml-2">

docs/conf.py

@@ -86,7 +86,7 @@ author = 'Alexander Graf and Andre Koch-Kramer'
 #
 # This is also used if you do content translation via gettext catalogs.
 # Usually you set "language" from the command line for these cases.
-language = None
+language = "en"
 
 # There are two options for replacing |today|: either, you set today to some
 # non-false value, then it is used: