[docs] [issue32995] Add a glossary entry for context variables

[Vinodhini]

Change by Vinodhini <me.vinob at gmail.com>:


----------
keywords: +patch
pull_requests: +9128
stage:  -> patch review

_______________________________________
Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue32995>
_______________________________________