chore(docs): add SM 3.9 docs page

Author: Michal-Leszczynski

docs/source/conf.py

@@ -10,9 +10,9 @@
 
 # Build documentation for the following tags and branches
 TAGS = []
-BRANCHES = ['master', 'branch-3.6', 'branch-3.7', 'branch-3.8']
+BRANCHES = ['master', 'branch-3.7', 'branch-3.8', 'branch-3.9']
 # Set the latest version.
-LATEST_VERSION = 'branch-3.8'
+LATEST_VERSION = 'branch-3.9'
 # Set which versions are not released yet.
 UNSTABLE_VERSIONS = ['master']
 # Set which versions are deprecated