Feature: Document that we have Docs Analytics using Plausible

[Mariatta]

Describe the enhancement or feature you would like

We have analytics information for CPython docs using Plausible, but this info doesn't seem to be easily discoverable. I found the link to it by searching on the Docs Community Discord chat messages. It would be nice to have a link to it on Devguide.

Link to CPython's docs metrics on Plausible: https://plausible.io/docs.python.org

Describe alternatives you have considered

No response

Additional context

No response