Add versions to doc theme

docs/partials/header.html

@@ -49,4 +49,6 @@
     </nav>
     <!-- Place this tag in your head or just before your close body tag. -->
     <script async defer src="https://buttons.github.io/buttons.js"></script>
-</header>
+    <script src="https://code.jquery.com/jquery-3.4.1.min.js"
+        integrity="sha256-CSXorXvZcTkaix6Yvo6HppcZGetbYMGWSFlBw8HfCJo=" crossorigin="anonymous"></script>
+</header>

docs/stylesheets/ft.extra.css

@@ -0,0 +1,14 @@
+.rst-versions  {
+    font-size: .7rem;
+    color: white;
+}
+
+.rst-versions.rst-badge .rst-current-version {
+    font-size: .7rem;
+    color: white;
+}
+
+.rst-versions .rst-other-versions {
+    color: white;
+    text-decoration: underline;
+}

mkdocs.yml

@@ -32,6 +32,8 @@ theme:
   palette:
     primary: 'blue grey'
     accent: 'tear'
+extra_css:
+  - 'stylesheets/ft.extra.css'
 markdown_extensions:
     - admonition
     - codehilite: