Issue #26355: Specify canonical URLs in docs pages

Add canonical header link on each page to corresponding major
version of the documentation.

Patch by Matthias Bussonnier.
diff --git a/Misc/ACKS b/Misc/ACKS
index 59b7704..3c169d6 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -218,6 +218,7 @@
 Tarn Weisner Burton
 Lee Busby
 Katherine Busch
+Matthias Bussonnier
 Ralph Butler
 Laurent De Buyst
 Zach Byrne
diff --git a/Misc/NEWS b/Misc/NEWS
index 8419915..fa0e740 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -70,6 +70,9 @@
 Documentation
 -------------
 
+- Issue #26355: Add canonical header link on each page to corresponding major
+  version of the documentation. Patch by Matthias Bussonnier.
+
 - Issue #29349: Fix Python 2 syntax in code for building the documentation.