add version nuber ack

Author: rflamary

docs/source/_templates/versions.html

@@ -3,7 +3,7 @@
   <!--  add shift_up to the class for force viewing ,
   data-toggle="rst-current-version" -->
     <span class="rst-current-version"  style="margin-bottom:1mm;">
-      <span class="fa fa-book"> Python Optimal Transport</span>
+      <span class="fa fa-book"> Python Optimal Transport</span> {{ version }}
       <hr  style="margin-bottom:1.5mm;margin-top:5mm;">
      <!--  versions
       <span class="fa fa-caret-down"></span>-->

docs/source/conf.py

@@ -162,7 +162,7 @@ def __getattr__(cls, name):
 # further.  For a list of options available for each theme, see the
 # documentation.
 
-html_theme_options = {}
+html_theme_options = {"version_selector": True}
 
 # Add any paths that contain custom themes here, relative to this directory.
 # html_theme_path = []