doc: conf: add release version 3.2.0

Add release version 3.2.0 to the documentation version list.

Signed-off-by: Fabio Baltieri <fabiobaltieri@google.com>
diff --git a/doc/conf.py b/doc/conf.py
index d221880..e77d0f5 100644
--- a/doc/conf.py
+++ b/doc/conf.py
@@ -160,6 +160,7 @@
     "current_version": version,
     "versions": (
         ("latest", "/"),
+        ("3.2.0", "/3.2.0/"),
         ("3.1.0", "/3.1.0/"),
         ("3.0.0", "/3.0.0/"),
         ("2.7.0", "/2.7.0/"),