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